diff --git a/modules/openapi-generator/src/main/resources/kotlin-multiplatform-client/api.mustache b/modules/openapi-generator/src/main/resources/kotlin-multiplatform-client/api.mustache
index 03c2376f5c9f..a17a3b42beb6 100644
--- a/modules/openapi-generator/src/main/resources/kotlin-multiplatform-client/api.mustache
+++ b/modules/openapi-generator/src/main/resources/kotlin-multiplatform-client/api.mustache
@@ -159,6 +159,7 @@ public open class {{classname}} : ApiClientBase {
             {{#bodyParam}}
 
             // Body
+            contentType(ContentType.Application.Json)
             {{#required}}
             this.body = {{{paramName}}}
             {{/required}}