diff --git a/components/style/properties/longhands/position.mako.rs b/components/style/properties/longhands/position.mako.rs
index 2e9517cc853..725f0862a99 100644
--- a/components/style/properties/longhands/position.mako.rs
+++ b/components/style/properties/longhands/position.mako.rs
@@ -75,6 +75,7 @@ ${helpers.single_keyword(
     extra_prefixes="webkit",
     animation_value_type="discrete",
     servo_restyle_damage = "reflow",
+    gecko_enum_prefix = "StyleFlexDirection",
 )}
 
 ${helpers.single_keyword(