diff --git a/overlay.nix b/overlay.nix
index 122729de0fdc9ac97ec903c039bb438d92958ad6..bda4332a081fcd8c713733a27a02f0dc312cd32c 100644
--- a/overlay.nix
+++ b/overlay.nix
@@ -1,18 +1,23 @@
-# You can use this file as a nixpkgs overlay. This is useful in the
-# case where you don't want to add the whole NUR namespace to your
-# configuration.
+# You can use this file as a nixpkgs overlay.
+# It's useful in the case where you don't want to add the whole NUR namespace
+# to your configuration.
 
 self: super:
 
 let
+  filterSet =
+    (f: g: s: builtins.listToAttrs
+      (map
+        (n: { name = n; value = builtins.getAttr n s; })
+        (builtins.filter
+          (n: f n && g (builtins.getAttr n s))
+          (builtins.attrNames s)
+        )
+      )
+    );
+  isReserved = n: builtins.elem n ["lib" "overlays" "modules"];
+in filterSet
+     (n: !(isReserved n)) # filter out non-packages
+     (p: true) # all packages are ok
+     (import ./default.nix { pkgs = super; })
 
-  isReserved = n: n == "lib" || n == "overlays" || n == "modules";
-  nameValuePair = n: v: { name = n; value = v; };
-  nurAttrs = import ./default.nix { pkgs = super; };
-
-in
-
-  builtins.listToAttrs
-  (map (n: nameValuePair n nurAttrs.${n})
-  (builtins.filter (n: !isReserved n)
-  (builtins.attrNames nurAttrs)))