diff --git a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-retrofit2/infrastructure/ApiClient.kt.mustache b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-retrofit2/infrastructure/ApiClient.kt.mustache
index d62d00f659c..dcb48ec8296 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-retrofit2/infrastructure/ApiClient.kt.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm-retrofit2/infrastructure/ApiClient.kt.mustache
@@ -132,7 +132,7 @@ import okhttp3.MediaType.Companion.toMediaType
         authNames: Array<String>
     ) : this(baseUrl, okHttpClientBuilder{{^kotlinx_serialization}}, serializerBuilder{{/kotlinx_serialization}}) {
         authNames.forEach { authName ->
-            val auth = when (authName) { {{#authMethods}}
+            val auth: Interceptor? = when (authName) { {{#authMethods}}
                 {{#isBasicBasic}}"{{name}}" -> HttpBasicAuth()
                 {{/isBasicBasic}}{{#isBasicBearer}}"{{name}}" -> HttpBearerAuth("{{scheme}}")
                 {{/isBasicBearer}}{{#isApiKey}}"{{name}}" -> ApiKeyAuth({{#isKeyInHeader}}"header"{{/isKeyInHeader}}{{#isKeyInQuery}}"query"{{/isKeyInQuery}}{{#isKeyInCookie}}"cookie"{{/isKeyInCookie}}, "{{keyParamName}}")
diff --git a/samples/client/petstore/kotlin-jvm-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-jvm-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 4621cb35f4f..0e89b1cbb56 100644
--- a/samples/client/petstore/kotlin-jvm-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-jvm-jackson/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -70,7 +70,7 @@ class ApiClient(
         authNames: Array<String>
     ) : this(baseUrl, okHttpClientBuilder, serializerBuilder) {
         authNames.forEach { authName ->
-            val auth = when (authName) { 
+            val auth: Interceptor? = when (authName) { 
                 "petstore_auth" -> OAuth(OAuthFlow.implicit, "http://petstore.swagger.io/api/oauth/dialog", "", "write:pets, read:pets")
                 
                 "api_key" -> ApiKeyAuth("header", "api_key")
diff --git a/samples/client/petstore/kotlin-retrofit2-kotlinx_serialization/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-retrofit2-kotlinx_serialization/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 884b2e66c28..d2a8cf9ce38 100644
--- a/samples/client/petstore/kotlin-retrofit2-kotlinx_serialization/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-retrofit2-kotlinx_serialization/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -72,7 +72,7 @@ class ApiClient(
         authNames: Array<String>
     ) : this(baseUrl, okHttpClientBuilder) {
         authNames.forEach { authName ->
-            val auth = when (authName) { 
+            val auth: Interceptor? = when (authName) { 
                 "petstore_auth" -> OAuth(OAuthFlow.implicit, "http://petstore.swagger.io/api/oauth/dialog", "", "write:pets, read:pets")
                 
                 "api_key" -> ApiKeyAuth("header", "api_key")
diff --git a/samples/client/petstore/kotlin-retrofit2-rx3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-retrofit2-rx3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 3c1dfd67345..9dfc8903789 100644
--- a/samples/client/petstore/kotlin-retrofit2-rx3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-retrofit2-rx3/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -74,7 +74,7 @@ class ApiClient(
         authNames: Array<String>
     ) : this(baseUrl, okHttpClientBuilder, serializerBuilder) {
         authNames.forEach { authName ->
-            val auth = when (authName) { 
+            val auth: Interceptor? = when (authName) { 
                 "petstore_auth" -> OAuth(OAuthFlow.implicit, "http://petstore.swagger.io/api/oauth/dialog", "", "write:pets, read:pets")
                 
                 "api_key" -> ApiKeyAuth("header", "api_key")
diff --git a/samples/client/petstore/kotlin-retrofit2/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt b/samples/client/petstore/kotlin-retrofit2/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
index 0d0605bbb60..e41d6a99f53 100644
--- a/samples/client/petstore/kotlin-retrofit2/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+++ b/samples/client/petstore/kotlin-retrofit2/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
@@ -72,7 +72,7 @@ class ApiClient(
         authNames: Array<String>
     ) : this(baseUrl, okHttpClientBuilder, serializerBuilder) {
         authNames.forEach { authName ->
-            val auth = when (authName) { 
+            val auth: Interceptor? = when (authName) { 
                 "petstore_auth" -> OAuth(OAuthFlow.implicit, "http://petstore.swagger.io/api/oauth/dialog", "", "write:pets, read:pets")
                 
                 "api_key" -> ApiKeyAuth("header", "api_key")