diff --git a/indexedDb/init.go b/indexedDb/init.go
index 9f107ba0cb695e42b41f8d133f261a0703c58ce9..81676053b9998d89e81bc1136b9bdba4b8092360 100644
--- a/indexedDb/init.go
+++ b/indexedDb/init.go
@@ -102,8 +102,13 @@ func v1Upgrade(db *idb.Database) error {
 	if err != nil {
 		return err
 	}
+
+	messageStoreMessageIndexOpts := idb.IndexOptions{
+		Unique:     true,
+		MultiEntry: false,
+	}
 	_, err = messageStore.CreateIndex(messageStoreMessageIndex,
-		js.ValueOf(messageStoreMessage), indexOpts)
+		js.ValueOf(messageStoreMessage), messageStoreMessageIndexOpts)
 	if err != nil {
 		return err
 	}