diff --git a/modules/graphical.nix b/modules/graphical.nix
index 6d47d92..8bb3ce7 100644
--- a/modules/graphical.nix
+++ b/modules/graphical.nix
@@ -30,6 +30,7 @@
         DisableFormHistory = true;
         SearchSuggestEnabled = false;
         Preferences = {
+          "dom.security.https_only_mode" = { Status = "locked"; Value = true; };
           "extensions.formautofill.available" = { Status = "locked"; Value = "off"; };
           "browser.contentblocking.category" = { Status = "locked"; Value = "strict"; };
           "network.IDN_show_punycode" = { Status = "locked"; Value = true; };