diff --git a/overlays/nixpak/firefox.nix b/overlays/nixpak/firefox.nix
index 38b26cb..ae4c168 100644
--- a/overlays/nixpak/firefox.nix
+++ b/overlays/nixpak/firefox.nix
@@ -75,5 +75,5 @@
       };
     };
   in
-    sandboxed-firefox-esr.config.env;
+    final.callPackage sandboxed-firefox-esr.config.env;
 }