diff --git a/pkgs/build-support/rust/default.nix b/pkgs/build-support/rust/default.nix
index 2b32da11d1c..37ea264a53f 100644
--- a/pkgs/build-support/rust/default.nix
+++ b/pkgs/build-support/rust/default.nix
@@ -80,5 +80,5 @@ in stdenv.mkDerivation (args // {
     runHook postInstall
   '';
 
-  passthru = { inherit cargoDeps; };
+  passthru = { inherit cargoDeps; } // (args.passthru or {});
 })