diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiResponse.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiResponse.kt.mustache
index ae7f7f4a11f..bcfe2e4b38e 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiResponse.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-okhttp/infrastructure/ApiResponse.kt.mustache
@@ -39,5 +39,5 @@ package {{packageName}}.infrastructure
     {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}val message: String? = null,
     {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/others/kotlin-jvm-okhttp-parameter-tests/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/others/kotlin-jvm-okhttp-parameter-tests/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/others/kotlin-jvm-okhttp-parameter-tests/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/others/kotlin-jvm-okhttp-parameter-tests/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-allOff-discriminator/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-array-simple-string-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-bigdecimal-default-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-enum-default-value/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-enum-default-value/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-enum-default-value/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-enum-default-value/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-explicit/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-explicit/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index 92b6205c6d6..4e422fa2ed7 100644
--- a/samples/client/petstore/kotlin-explicit/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-explicit/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ public class ServerError<T>(
     public val message: String? = null,
     public val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-gson/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-json-request-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-json-request-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-json-request-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-json-request-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-jvm-okhttp4-coroutines/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-kotlinx-datetime/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-kotlinx-datetime/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-kotlinx-datetime/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-kotlinx-datetime/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-modelMutable/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-modelMutable/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-modelMutable/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-modelMutable/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-moshi-codegen/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-moshi-codegen/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-moshi-codegen/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-moshi-codegen/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-name-parameter-mappings/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-name-parameter-mappings/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-name-parameter-mappings/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-name-parameter-mappings/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-nonpublic/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-nonpublic/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index 64824828dd4..168b38d58b1 100644
--- a/samples/client/petstore/kotlin-nonpublic/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-nonpublic/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ internal class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index 20ac25b1250..3a363989d43 100644
--- a/samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-string/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-threetenbp/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin-uppercase-enum/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)
diff --git a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
index cf2cfaa95d9..689fb03cd7a 100644
--- a/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+++ b/samples/client/petstore/kotlin/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
@@ -39,5 +39,5 @@ class ServerError<T>(
     val message: String? = null,
     val body: Any? = null,
     override val statusCode: Int = -1,
-    override val headers: Map<String, List<String>>
+    override val headers: Map<String, List<String>> = mapOf()
 ): ApiResponse<T>(ResponseType.ServerError)