diff --git a/modules/openapi-generator/src/main/resources/csharp-netcore/ClientUtils.mustache b/modules/openapi-generator/src/main/resources/csharp-netcore/ClientUtils.mustache
index b407a4edd08..f756a2c86ae 100755
--- a/modules/openapi-generator/src/main/resources/csharp-netcore/ClientUtils.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp-netcore/ClientUtils.mustache
@@ -169,7 +169,7 @@ namespace {{packageName}}.Client
         public static String SelectHeaderContentType(String[] contentTypes)
         {
             if (contentTypes.Length == 0)
-                return "application/json";
+                return null;
 
             foreach (var contentType in contentTypes)
             {
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/ClientUtils.cs
index 9bd20d5f576..65d7da67f6a 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -174,7 +174,7 @@ namespace Org.OpenAPITools.Client
         public static String SelectHeaderContentType(String[] contentTypes)
         {
             if (contentTypes.Length == 0)
-                return "application/json";
+                return null;
 
             foreach (var contentType in contentTypes)
             {
diff --git a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/ClientUtils.cs
index 9bd20d5f576..65d7da67f6a 100644
--- a/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp-netcore/OpenAPIClientCore/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -174,7 +174,7 @@ namespace Org.OpenAPITools.Client
         public static String SelectHeaderContentType(String[] contentTypes)
         {
             if (contentTypes.Length == 0)
-                return "application/json";
+                return null;
 
             foreach (var contentType in contentTypes)
             {