diff --git a/firefox/user.js b/firefox/user.js
index 6901e23..8bccc77 100644
--- a/firefox/user.js
+++ b/firefox/user.js
@@ -16,6 +16,8 @@ user_pref("datareporting.policy.dataSubmissionEnabled", false);
 user_pref("device.sensors.enabled", false);
 user_pref("dom.push.connection.enabled", false);
 user_pref("dom.push.enabled", false);
+user_pref("dom.security.https_only_mode", true);
+user_pref("dom.security.https_only_mode_ever_enabled", true);
 user_pref("dom.webnotifications.enabled", false);
 user_pref("experiments.enabled", false);
 user_pref("experiments.manifest.uri", "");