diff --git a/fdbclient/include/fdbclient/ClusterInterface.h b/fdbclient/include/fdbclient/ClusterInterface.h
index a88a721757..a4e3da44f3 100644
--- a/fdbclient/include/fdbclient/ClusterInterface.h
+++ b/fdbclient/include/fdbclient/ClusterInterface.h
@@ -114,7 +114,7 @@ struct OpenDatabaseRequest {
 
 		template <typename Ar>
 		void serialize(Ar& ar) {
-			serializer(ar, samples);
+			serializer(ar, count, samples);
 		}
 
 		// Merges a set of Samples into *this