diff --git a/src/main/java/io/swagger/codegen/v3/generators/DefaultCodegenConfig.java b/src/main/java/io/swagger/codegen/v3/generators/DefaultCodegenConfig.java
index d6f59b9711..e4ff43f023 100644
--- a/src/main/java/io/swagger/codegen/v3/generators/DefaultCodegenConfig.java
+++ b/src/main/java/io/swagger/codegen/v3/generators/DefaultCodegenConfig.java
@@ -3770,7 +3770,9 @@ protected Schema getSchemaFromResponse(ApiResponse response) {
         Schema schema = null;
         for (String contentType : response.getContent().keySet()) {
             schema = response.getContent().get(contentType).getSchema();
-            schema.addExtension("x-content-type", contentType);
+            if (schema != null) {
+                schema.addExtension("x-content-type", contentType);
+            }
             break;
         }
         return schema;