diff --git a/test/netstd/Client/Program.cs b/test/netstd/Client/Program.cs
index 72139d9..8d973c4 100644
--- a/test/netstd/Client/Program.cs
+++ b/test/netstd/Client/Program.cs
@@ -52,6 +52,7 @@
                     PrintHelp();
                     return 0;
                 default:
+                    Console.WriteLine("Invalid argument: {0}", firstArg);
                     PrintHelp();
                     return -1;
             }