diff --git a/pkgs/development/haskell-modules/generic-builder.nix b/pkgs/development/haskell-modules/generic-builder.nix
index c633310a37a4..e4ae24f74fab 100644
--- a/pkgs/development/haskell-modules/generic-builder.nix
+++ b/pkgs/development/haskell-modules/generic-builder.nix
@@ -243,7 +243,7 @@ stdenv.mkDerivation ({
     # libraries) from all the dependencies.
     local dynamicLinksDir="$out/lib/links"
     mkdir -p $dynamicLinksDir
-    for d in $(grep dynamic-library-dirs "$packageConfDir/"*|awk '{print $2}'); do
+    for d in $(grep dynamic-library-dirs "$packageConfDir/"*|awk '{print $2}'|sort -u); do
       ln -s "$d/"*.dylib $dynamicLinksDir
     done
     # Edit the local package DB to reference the links directory.