diff --git a/builder.nix b/builder.nix
index 7e65ffb..5ecf5c2 100644
--- a/builder.nix
+++ b/builder.nix
@@ -12,7 +12,12 @@ let
     with builtins;
     let
       # Funktionalise pkgs; our main entry point to resolve default*nix build scripts.
-      funcPkgs = { __functor = self: arg: resolve arg; } // pkgs;
+      getSrc = filterSource
+        (path: type: baseNameOf path != ".git" && baseNameOf path != ".envrc" && (all (x: path != x) filter));
+      funcPkgs = {
+        __functor = self: arg: resolve arg;
+        redo.getSrc = getSrc;
+      } // pkgs;
 
       _builder = let
         imported = (tryEval (let
@@ -22,9 +27,7 @@ let
       in if imported.success
          then imported.value
          else {
-           src = filterSource
-             (path: type: baseNameOf path != ".git" && baseNameOf path != ".envrc" && (all (x: path != x) filter))
-             (/. + root);
+           src = getSrc (/. + root);
            builder = let
              relPath = dirOf (removePrefix (root + "/") builder);
            in ''