diff --git a/style/properties/longhands.toml b/style/properties/longhands.toml
index 1b50d63938..eb9f39663b 100644
--- a/style/properties/longhands.toml
+++ b/style/properties/longhands.toml
@@ -2182,7 +2182,7 @@ affects = "overflow"
 type = "UserSelect"
 initial = "computed::UserSelect::Auto"
 struct = "ui"
-engine = "gecko"
+servo_pref = "layout.unimplemented"
 extra_prefixes = ["moz", "webkit"]
 animation_type = "discrete"
 spec = "https://drafts.csswg.org/css-ui-4/#propdef-user-select"