diff --git a/overlays/nixpak/firefox.nix b/overlays/nixpak/firefox.nix
index 68783ff..2da8db0 100644
--- a/overlays/nixpak/firefox.nix
+++ b/overlays/nixpak/firefox.nix
@@ -75,7 +75,7 @@
       };
     };
   in
-    prev.wrapFirefox (sandboxed-firefox-esr.config.env // {
+    prev.wrapFirefox (sandboxed-firefox-esr.config.env {
       inherit (prev.firefox-esr) stdenv lib callPackage fetchurl nixosTests buildMozillaMach;
     }) {
       nameSuffix = "-esr";