diff --git a/pkgs/development/tools/parsing/bison/bison-2.4.nix b/pkgs/development/tools/parsing/bison/bison-2.4.nix
index b188c77e99f..09596f173d0 100644
--- a/pkgs/development/tools/parsing/bison/bison-2.4.nix
+++ b/pkgs/development/tools/parsing/bison/bison-2.4.nix
@@ -10,8 +10,6 @@ stdenv.mkDerivation rec {
 
   buildInputs = [m4];
 
-  x = "z";
-
   doCheck = true;
 
   meta = {