diff --git a/Program.cs b/Program.cs
index 9cb8db0..722b0c7 100644
--- a/Program.cs
+++ b/Program.cs
@@ -405,6 +405,10 @@ namespace IngameScript
                     Undock();
                 }
             }
+            else
+            {
+                Echo("Invalid argument.");
+            }
         }
     }
 }