diff --git a/firefox.js b/firefox.js
index d4ed3ab..da6acf7 100644
--- a/firefox.js
+++ b/firefox.js
@@ -29,3 +29,6 @@ user_pref("browser.backspace_action", 0);
 
 // Ctrl-Tab should not use recent order (it's confusing for me)
 user_pref("browser.ctrlTab.recentlyUsedOrder", false);
+
+// Don't display fullscreen warning
+user_pref("full-screen-api.warning.timeout", 0)