diff --git a/components/style/properties/longhands/position.mako.rs b/components/style/properties/longhands/position.mako.rs
index 25354ab19af..48976a8f123 100644
--- a/components/style/properties/longhands/position.mako.rs
+++ b/components/style/properties/longhands/position.mako.rs
@@ -145,7 +145,7 @@ ${helpers.single_keyword(
         "align-items",
         "stretch flex-start flex-end center baseline",
         engines="servo-2013 servo-2020",
-        servo_2020_pref="layout.2020.unimplemented",
+        servo_2020_pref="layout.flexbox.enabled",
         extra_prefixes="webkit",
         spec="https://drafts.csswg.org/css-flexbox/#align-items-property",
         animation_value_type="discrete",
@@ -234,7 +234,7 @@ ${helpers.predefined_type(
         "align-self",
         "auto stretch flex-start flex-end center baseline",
         engines="servo-2013 servo-2020",
-        servo_2020_pref="layout.2020.unimplemented",
+        servo_2020_pref="layout.flexbox.enabled",
         extra_prefixes="webkit",
         spec="https://drafts.csswg.org/css-flexbox/#propdef-align-self",
         animation_value_type="discrete",