diff --git a/packages/utils/src/syncpromise.ts b/packages/utils/src/syncpromise.ts
index 8612e494c8ca..3102a3b67d2b 100644
--- a/packages/utils/src/syncpromise.ts
+++ b/packages/utils/src/syncpromise.ts
@@ -5,7 +5,7 @@
 import { isThenable } from './is';
 
 /** SyncPromise internal states */
-enum States {
+const enum States {
   /** Pending */
   PENDING = 'PENDING',
   /** Resolved / OK */