diff --git a/proto/vectorindex.proto b/proto/vectorindex.proto
index c9f4acf..06cd4aa 100644
--- a/proto/vectorindex.proto
+++ b/proto/vectorindex.proto
@@ -245,5 +245,5 @@ message _CountItemsRequest {
 }
 
 message _CountItemsResponse {
-    uint32 item_count = 1;
+    uint64 item_count = 1;
 }