diff --git a/pkgs/dockerImage.nix b/pkgs/dockerImage.nix
index ff882c8..bd4706f 100644
--- a/pkgs/dockerImage.nix
+++ b/pkgs/dockerImage.nix
@@ -1,8 +1,7 @@
 { sources ? import ./nix/sources.nix, pkgs ? import sources.nixpkgs { } }:
 
 attrs:
-pkgs.dockerTools.buildLayeredImage {
-  config = {
-    WorkingDir = "/";
-  };
-} // attrs
+let
+  default = { config.WorkingDir = "/"; };
+  input = (default // attrs);
+in pkgs.dockerTools.buildLayeredImage input