diff --git a/pkgs/development/haskell-modules/configuration-common.nix b/pkgs/development/haskell-modules/configuration-common.nix
index 705da4df466..76675ef8755 100644
--- a/pkgs/development/haskell-modules/configuration-common.nix
+++ b/pkgs/development/haskell-modules/configuration-common.nix
@@ -151,11 +151,11 @@ self: super: {
   wai-test = dontHaddock super.wai-test;
   zlib-conduit = dontHaddock super.zlib-conduit;
 
-  # jailbreak doesn't get the job done because the Cabal file uses conditionals a lot.
-  darcs = overrideCabal super.darcs (drv: {
+  # Jailbreak doesn't get the job done because the Cabal file uses conditionals a lot.
+  darcs = (overrideCabal super.darcs (drv: {
     doCheck = false;            # The test suite won't even start.
-    patchPhase = "sed -i -e 's|attoparsec.*,|attoparsec,|' darcs.cabal";
-  });
+    patchPhase = "sed -i -e 's|attoparsec .*,|attoparsec,|' darcs.cabal";
+  })).overrideScope (self: super: { zlib = self.zlib_0_5_4_2; });
 
   # https://github.com/massysett/rainbox/issues/1
   rainbox = dontCheck super.rainbox;