diff --git a/css-layout-api/Overview.bs b/css-layout-api/Overview.bs
index 899f1cee..4ff3b7c5 100644
--- a/css-layout-api/Overview.bs
+++ b/css-layout-api/Overview.bs
@@ -1594,7 +1594,7 @@ dictionary FragmentResultOptions {
     BreakTokenOptions breakToken = null;
 };
 
-[Constructor(FragmentResultOptions)]
+[Constructor(optional FragmentResultOptions options)]
 interface FragmentResult {
     readonly attribute double inlineSize;
     readonly attribute double blockSize;