diff --git a/roles/desktop/firefox.nix b/roles/desktop/firefox.nix
index 797fd9e..76c431a 100644
--- a/roles/desktop/firefox.nix
+++ b/roles/desktop/firefox.nix
@@ -31,6 +31,10 @@
 					"Value" = true;
 					"Status" = "default";
 				};
+				"dom.security.https_only_mode" = {
+					"Value" = true;
+					"Status" = "locked";
+				};
 			};
 			"Permissions" = {
 				"Autoplay" = {