diff --git a/pkgs/development/libraries/haskell/monad-loops/default.nix b/pkgs/development/libraries/haskell/monad-loops/default.nix
index a58d90fc98b..350397f719d 100644
--- a/pkgs/development/libraries/haskell/monad-loops/default.nix
+++ b/pkgs/development/libraries/haskell/monad-loops/default.nix
@@ -2,8 +2,8 @@
 
 cabal.mkDerivation (self: {
   pname = "monad-loops";
-  version = "0.4.2";
-  sha256 = "08sz08p4z1p78dv7rmsqvin59h19i6i07sp7jg3zwxwjxa76fds8";
+  version = "0.4.2.1";
+  sha256 = "1dprwndc0bxzpmrkj1xb9kzjrg3i06zsg43yaabn5x5gcaj8is56";
   meta = {
     homepage = "https://github.com/mokus0/monad-loops";
     description = "Monadic loops";