diff --git a/2004/kopczynski/README.md b/2004/kopczynski/README.md
index 20812b414..2ad4a6711 100644
--- a/2004/kopczynski/README.md
+++ b/2004/kopczynski/README.md
@@ -18,7 +18,7 @@ will not work with it enabled.
 ## Try:
 
 ```sh
-./try
+./try.sh
 ```
 
 What happens if you feed the program source to the program? Can you figure out