diff --git a/pkgs/build-support/fetchfirefoxaddon/default.nix b/pkgs/build-support/fetchfirefoxaddon/default.nix
index 4b7c68484d2e..1f50876ce2d4 100644
--- a/pkgs/build-support/fetchfirefoxaddon/default.nix
+++ b/pkgs/build-support/fetchfirefoxaddon/default.nix
@@ -12,7 +12,7 @@ stdenv.mkDerivation rec {
   inherit name;
   extid = "${src.outputHash}@${name}";
   passthru = {
-    exitd=extid;
+    inherit extid;
   };
 
   builder = writeScript "xpibuilder" ''