diff --git a/index.bs b/index.bs
index 05ff2b82..0ea3f54a 100644
--- a/index.bs
+++ b/index.bs
@@ -1166,7 +1166,7 @@ enum MLOperandDataType {
 
 dictionary MLOperandDescriptor {
   required MLOperandDataType dataType;
-  sequence<[EnforceRange] unsigned long> shape = [];
+  required sequence<[EnforceRange] unsigned long> shape;
 };
 </script>