diff --git a/overlays/nixpak/firefox.nix b/overlays/nixpak/firefox.nix
index 2c8d14a..2e4dd95 100644
--- a/overlays/nixpak/firefox.nix
+++ b/overlays/nixpak/firefox.nix
@@ -6,7 +6,9 @@
   firefox-esr = let
     sandboxed-firefox-esr = prev.mkNixPak {
       config = { sloth, ... }: {
-        app.package = prev.firefox-esr-unwrapped;
+        app.package = prev.firefox-esr-unwrapped.override {
+          privateLib = true;
+        };
         app.binPath = "bin/firefox-esr";
         flatpak.appId = "org.mozilla.firefox";