diff --git a/default.nix b/default.nix
index 72ae4b0..ef5f20e 100644
--- a/default.nix
+++ b/default.nix
@@ -1,3 +1,13 @@
-{ haskellPackages }:
+{ lib, haskellPackages }:
 
-haskellPackages.callCabal2nix "xmonad-masser" ./. {}
+let
+  filtered = src: lib.sourceByRegex src [
+    "^src.*"
+    "Setup.hs"
+    ".*cabal"
+    "LICENSE"
+    ];
+
+in
+
+haskellPackages.callCabal2nix "xmonad-masser" (filtered ./.) {}