diff --git a/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache b/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache
index 6a12dbfbb9c..0bddc657e0d 100644
--- a/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache
@@ -1356,7 +1356,7 @@ public class ApiClient {
                 reqBody = null;
             } else {
                 // use an empty request body (for POST, PUT and PATCH)
-                reqBody = RequestBody.create("", MediaType.parse(contentType));
+                reqBody = RequestBody.create("", contentType == null ? null : MediaType.parse(contentType));
             }
         } else {
             reqBody = serialize(body, contentType);
diff --git a/samples/client/others/java/okhttp-gson-streaming/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/others/java/okhttp-gson-streaming/src/main/java/org/openapitools/client/ApiClient.java
index 81d09b9e78d..20c24352d3d 100644
--- a/samples/client/others/java/okhttp-gson-streaming/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/others/java/okhttp-gson-streaming/src/main/java/org/openapitools/client/ApiClient.java
@@ -1151,7 +1151,7 @@ public class ApiClient {
                 reqBody = null;
             } else {
                 // use an empty request body (for POST, PUT and PATCH)
-                reqBody = RequestBody.create("", MediaType.parse(contentType));
+                reqBody = RequestBody.create("", contentType == null ? null : MediaType.parse(contentType));
             }
         } else {
             reqBody = serialize(body, contentType);
diff --git a/samples/client/petstore/java/okhttp-gson-dynamicOperations/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/okhttp-gson-dynamicOperations/src/main/java/org/openapitools/client/ApiClient.java
index f5c30aa086b..c065d7d109f 100644
--- a/samples/client/petstore/java/okhttp-gson-dynamicOperations/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/okhttp-gson-dynamicOperations/src/main/java/org/openapitools/client/ApiClient.java
@@ -1229,7 +1229,7 @@ public class ApiClient {
                 reqBody = null;
             } else {
                 // use an empty request body (for POST, PUT and PATCH)
-                reqBody = RequestBody.create("", MediaType.parse(contentType));
+                reqBody = RequestBody.create("", contentType == null ? null : MediaType.parse(contentType));
             }
         } else {
             reqBody = serialize(body, contentType);
diff --git a/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/ApiClient.java
index 8f45483a566..8ae5d16c3ba 100644
--- a/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/ApiClient.java
@@ -1230,7 +1230,7 @@ public class ApiClient {
                 reqBody = null;
             } else {
                 // use an empty request body (for POST, PUT and PATCH)
-                reqBody = RequestBody.create("", MediaType.parse(contentType));
+                reqBody = RequestBody.create("", contentType == null ? null : MediaType.parse(contentType));
             }
         } else {
             reqBody = serialize(body, contentType);
diff --git a/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/ApiClient.java
index e551cddfc65..0e626694f6f 100644
--- a/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/ApiClient.java
@@ -1249,7 +1249,7 @@ public class ApiClient {
                 reqBody = null;
             } else {
                 // use an empty request body (for POST, PUT and PATCH)
-                reqBody = RequestBody.create("", MediaType.parse(contentType));
+                reqBody = RequestBody.create("", contentType == null ? null : MediaType.parse(contentType));
             }
         } else {
             reqBody = serialize(body, contentType);