diff --git a/components/style/gecko/non_ts_pseudo_class_list.rs b/components/style/gecko/non_ts_pseudo_class_list.rs
index 56e62b6de4b..04f57b73885 100644
--- a/components/style/gecko/non_ts_pseudo_class_list.rs
+++ b/components/style/gecko/non_ts_pseudo_class_list.rs
@@ -47,7 +47,7 @@ macro_rules! apply_non_ts_list {
                 ("visited", Visited, visited, IN_VISITED_STATE, _),
                 ("active", Active, active, IN_ACTIVE_STATE, _),
                 ("checked", Checked, checked, IN_CHECKED_STATE, _),
-                ("defined", Defined, defined, IN_DEFINED_STATE, _),
+                ("defined", Defined, defined, IN_DEFINED_STATE, PSEUDO_CLASS_ENABLED_IN_UA_SHEETS_AND_CHROME),
                 ("disabled", Disabled, disabled, IN_DISABLED_STATE, _),
                 ("enabled", Enabled, enabled, IN_ENABLED_STATE, _),
                 ("focus", Focus, focus, IN_FOCUS_STATE, _),