diff --git a/pkgs/development/haskell-modules/generic-builder.nix b/pkgs/development/haskell-modules/generic-builder.nix
index 6b2926ef2d2..7d5a9dd5903 100644
--- a/pkgs/development/haskell-modules/generic-builder.nix
+++ b/pkgs/development/haskell-modules/generic-builder.nix
@@ -129,7 +129,7 @@ stdenv.mkDerivation ({
     export PATH="${ghc}/bin:$PATH"
     ${optionalString (hasActiveLibrary && hyperlinkSource) "export PATH=${hscolour}/bin:$PATH"}
 
-    packageConfDir="$TMP/package.conf.d"
+    packageConfDir="$TMPDIR/package.conf.d"
     mkdir -p $packageConfDir
 
     setupCompileFlags="${concatStringsSep " " setupCompileFlags}"