diff --git a/HACKING.md b/HACKING.md
index c88669761a47ea6954db1295c3c40cf7cc7817ba..4fe4d2c921811103b96628e048112b31f693cb1b 100644
--- a/HACKING.md
+++ b/HACKING.md
@@ -132,7 +132,7 @@ lost. But if the change is small and self contained, feel free to
 attach it to your email, and send it to `ghc-devs`.
 
 Furthermore, if you're a developer (or want to become one!) you're
-undoubtly also interested in the other mailing lists:
+undoubtedly also interested in the other mailing lists:
 
  * [glasgow-haskell-users](http://www.haskell.org/mailman/listinfo/glasgow-haskell-users)
    is where developers/users meet.