diff --git a/overlays/nixpak/firefox.nix b/overlays/nixpak/firefox.nix
index 38b26cb..bb4fbb6 100644
--- a/overlays/nixpak/firefox.nix
+++ b/overlays/nixpak/firefox.nix
@@ -75,5 +75,11 @@
       };
     };
   in
-    sandboxed-firefox-esr.config.env;
+    sandboxed-firefox-esr.config.env.overrideAttrs (old: {
+      override = args: sandboxed-firefox-esr.config.env.override (old: {
+        extraPrefsFiles = args.extraPrefsFiles or old.extraPrefsFiles or [];
+        nativeMessagingHosts = args.nativeMessagingHosts or old.nativeMessagingHosts or [];
+        inherit (args) cfg;
+      });
+    });
 }