diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java
index 67f41edc715..b37294c2a9d 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java
@@ -962,7 +962,9 @@ public class KotlinClientCodegen extends AbstractKotlinCodegen {
                         ).trim();
                         return "multipart/form-data".equals(mediaType)
                                 || "application/x-www-form-urlencoded".equals(mediaType)
-                                || (mediaType.startsWith("application/") && (mediaType.endsWith("json") || mediaType.endsWith("octet-stream")));
+                                || (mediaType.startsWith("application/") && mediaType.endsWith("json"))
+                                || "application/octet-stream".equals(mediaType)
+                                || "text/plain".equals(mediaType);
                     };
                     operation.consumes = operation.consumes == null ? null : operation.consumes.stream()
                             .filter(isSerializable)
diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiClient.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiClient.kt.mustache
index 2b8dcc1c5b6..bc0027e7405 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiClient.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiClient.kt.mustache
@@ -70,6 +70,7 @@ import com.squareup.moshi.adapter
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}val apiKey: MutableMap<String, String> = mutableMapOf()
         {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -209,10 +210,10 @@ import com.squareup.moshi.adapter
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     {{#moshi}}
@@ -298,7 +299,8 @@ import com.squareup.moshi.adapter
                 }}{{#kotlinx_serialization}}Serializer.kotlinxSerializationJson.decodeFromString<T>(bodyContent){{/kotlinx_serialization}}
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/others/kotlin-jvm-okhttp-parameter-tests/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/others/kotlin-jvm-okhttp-parameter-tests/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 92580a974dd..e59fa0b5a48 100644
--- a/samples/client/others/kotlin-jvm-okhttp-parameter-tests/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/others/kotlin-jvm-okhttp-parameter-tests/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 92580a974dd..e59fa0b5a48 100644
--- a/samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 92580a974dd..e59fa0b5a48 100644
--- a/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 92580a974dd..e59fa0b5a48 100644
--- a/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 92580a974dd..e59fa0b5a48 100644
--- a/samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-enum-default-value/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-enum-default-value/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 92580a974dd..e59fa0b5a48 100644
--- a/samples/client/petstore/kotlin-enum-default-value/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-enum-default-value/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-explicit/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-explicit/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 158ee6350bd..b76315bd9e8 100644
--- a/samples/client/petstore/kotlin-explicit/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-explicit/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ public open class ApiClient(public val baseUrl: String, public val client: Call.
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         public val apiKey: MutableMap<String, String> = mutableMapOf()
         public val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ public open class ApiClient(public val baseUrl: String, public val client: Call.
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ public open class ApiClient(public val baseUrl: String, public val client: Call.
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 42330f0a049..1911b1d4788 100644
--- a/samples/client/petstore/kotlin-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JsonMediaType): T? {
@@ -242,7 +243,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.gson.fromJson(bodyContent, (object: TypeToken<T>(){}).getType())
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index e72665e5548..44095e73f25 100644
--- a/samples/client/petstore/kotlin-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JsonMediaType): T? {
@@ -242,7 +243,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.jacksonObjectMapper.readValue(bodyContent, object: TypeReference<T>() {})
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-json-request-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-json-request-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 502a01ba2b9..70539f9c852 100644
--- a/samples/client/petstore/kotlin-json-request-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-json-request-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -43,6 +43,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -171,10 +172,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JsonMediaType): T? {
@@ -248,7 +249,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.kotlinxSerializationJson.decodeFromString<T>(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index e4c296b20e9..5a8f81566cf 100644
--- a/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -44,6 +44,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -172,10 +173,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JsonMediaType): T? {
@@ -245,7 +246,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.gson.fromJson(bodyContent, (object: TypeToken<T>(){}).getType())
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-kotlinx-datetime/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-kotlinx-datetime/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index b1cf2c6828c..0867fa0c317 100644
--- a/samples/client/petstore/kotlin-kotlinx-datetime/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-kotlinx-datetime/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-modelMutable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-modelMutable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index b1cf2c6828c..0867fa0c317 100644
--- a/samples/client/petstore/kotlin-modelMutable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-modelMutable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-moshi-codegen/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-moshi-codegen/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index b1cf2c6828c..0867fa0c317 100644
--- a/samples/client/petstore/kotlin-moshi-codegen/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-moshi-codegen/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-name-parameter-mappings/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-name-parameter-mappings/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 92580a974dd..e59fa0b5a48 100644
--- a/samples/client/petstore/kotlin-name-parameter-mappings/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-name-parameter-mappings/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-nonpublic/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-nonpublic/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 87f80e81ab0..ad481e08ba5 100644
--- a/samples/client/petstore/kotlin-nonpublic/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-nonpublic/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ internal open class ApiClient(val baseUrl: String, val client: Call.Factory = de
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ internal open class ApiClient(val baseUrl: String, val client: Call.Factory = de
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ internal open class ApiClient(val baseUrl: String, val client: Call.Factory = de
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index b1cf2c6828c..0867fa0c317 100644
--- a/samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index b1cf2c6828c..0867fa0c317 100644
--- a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 3ec87d33987..83cf91d8928 100644
--- a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 238f6dcca90..09a59bf60d7 100644
--- a/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -42,6 +42,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -170,10 +171,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     protected inline fun <reified T: Any?> responseBody(response: Response, mediaType: String? = JsonMediaType): T? {
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.kotlinxSerializationJson.decodeFromString<T>(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }
 
diff --git a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index b1cf2c6828c..0867fa0c317 100644
--- a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -41,6 +41,7 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
         protected const val FormUrlEncMediaType: String = "application/x-www-form-urlencoded"
         protected const val XmlMediaType: String = "application/xml"
         protected const val OctetMediaType: String = "application/octet-stream"
+        protected const val TextMediaType: String = "text/plain"
 
         val apiKey: MutableMap<String, String> = mutableMapOf()
         val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
@@ -169,10 +170,10 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                         .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
                 }
             mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
-            mediaType == OctetMediaType && content is ByteArray ->
-                content.toRequestBody(OctetMediaType.toMediaTypeOrNull())
+            mediaType == TextMediaType && content is String ->
+                content.toRequestBody(TextMediaType.toMediaTypeOrNull())
             // TODO: this should be extended with other serializers
-            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, byte body and File body.")
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body, text body, byte body and File body.")
         }
 
     @OptIn(ExperimentalStdlibApi::class)
@@ -243,7 +244,8 @@ open class ApiClient(val baseUrl: String, val client: Call.Factory = defaultClie
                 Serializer.moshi.adapter<T>().fromJson(bodyContent)
             }
             mediaType == OctetMediaType -> body.bytes() as? T
-            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+            mediaType == TextMediaType -> body.string() as? T
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body, text body and byte body.")
         }
     }