diff --git a/aspnet-core/modules/open-api/OpenApi.Sdk/OpenApi/ClientProxy.cs b/aspnet-core/modules/open-api/OpenApi.Sdk/OpenApi/ClientProxy.cs
index b132b10ad..1df55147b 100644
--- a/aspnet-core/modules/open-api/OpenApi.Sdk/OpenApi/ClientProxy.cs
+++ b/aspnet-core/modules/open-api/OpenApi.Sdk/OpenApi/ClientProxy.cs
@@ -153,7 +153,7 @@ namespace OpenApi
 
         private static string UrlEncode(string str)
         {
-            return HttpUtility.UrlEncode(str);
+            return HttpUtility.UrlEncode(str, Encoding.UTF8).ToUpper();
         }
     }
 }