diff --git a/nix/nimble.nix b/nix/nimble.nix
index 86262b7c..7dde65c5 100644
--- a/nix/nimble.nix
+++ b/nix/nimble.nix
@@ -4,6 +4,7 @@ let
   tools = pkgs.callPackage ./tools.nix {};
   nbsVersion = tools.findKeyValue "^[[:space:]]+NIMBLE_COMMIT='([a-f0-9]+)'.*$" ../vendor/nimbus-build-system/scripts/build_nim.sh;
   nimVersion = tools.findKeyValue "^ +NimbleStableCommit = \"([a-f0-9]+)\".+" ../vendor/nimbus-build-system/vendor/Nim/koch.nim;
+  sourceFile = ../vendor/nimbus-build-system/vendor/Nim/koch.nim;
 in pkgs.fetchFromGitHub {
   owner = "nim-lang";
   repo = "nimble";