diff --git a/docs/public/firefox/configure.rst b/docs/public/firefox/configure.rst
index 9415285..6d52349 100644
--- a/docs/public/firefox/configure.rst
+++ b/docs/public/firefox/configure.rst
@@ -9,5 +9,6 @@ Client certificates
 
 .. code:: js
 
+ user_pref("browser.tabs.closeWindowWithLastTab", false);
  user_pref("security.default_personal_cert", "Ask Every Time");
  user_pref("security.default_personal_cert", "Select Automatically");