diff --git a/pkgs/build-support/buildenv/default.nix b/pkgs/build-support/buildenv/default.nix
index 63e4481e4e3..293291dc1da 100644
--- a/pkgs/build-support/buildenv/default.nix
+++ b/pkgs/build-support/buildenv/default.nix
@@ -23,10 +23,12 @@
 
 , # Shell command to run after building the symlink tree.
   postBuild ? ""
+
+, passthru ? {}
 }:
 
 runCommand name
-  { inherit manifest paths ignoreCollisions pathsToLink postBuild;
+  { inherit manifest paths ignoreCollisions passthru pathsToLink postBuild;
     preferLocalBuild = true;
   }
   ''