diff --git a/pkgs/development/compilers/ghc/6.12.3.nix b/pkgs/development/compilers/ghc/6.12.3.nix
index f6beaf3a006..e480a6f837c 100644
--- a/pkgs/development/compilers/ghc/6.12.3.nix
+++ b/pkgs/development/compilers/ghc/6.12.3.nix
@@ -39,5 +39,6 @@ stdenv.mkDerivation rec {
     maintainers = with stdenv.lib.maintainers; [ marcweber andres simons ];
     platforms = ["x86_64-linux" "i686-linux"];  # Darwin is unsupported.
     inherit (ghc.meta) license;
+    broken = true; # broken by gcc 5.x: http://hydra.nixos.org/build/33627548
   };
 }