diff --git a/pkgs/development/tools/parsing/happy/1.19.2.nix b/pkgs/development/tools/parsing/happy/1.19.2.nix
index eaf027b591d..4173d6d6c11 100644
--- a/pkgs/development/tools/parsing/happy/1.19.2.nix
+++ b/pkgs/development/tools/parsing/happy/1.19.2.nix
@@ -8,6 +8,7 @@ cabal.mkDerivation (self: {
   isExecutable = true;
   buildDepends = [ mtl ];
   buildTools = [ perl ];
+  patchPhase = "sed -i -e '/^import Data.Monoid/d' Setup.lhs";
   meta = {
     homepage = "http://www.haskell.org/happy/";
     description = "Happy is a parser generator for Haskell";