diff --git a/typescript/types/clock_info.d.ts b/typescript/types/clock_info.d.ts
index ce8c78d72..9b664a6dc 100644
--- a/typescript/types/clock_info.d.ts
+++ b/typescript/types/clock_info.d.ts
@@ -20,7 +20,7 @@ declare module ClockInfo {
       hasRange: true,
       get(): RangeItem,
     } | {
-      hasRange: false,
+      hasRange?: false,
       get(): Item,
     }
   );