diff --git a/test/unit/persist_read_stubs.c b/test/unit/persist_read_stubs.c
index 7e0d18c4..568016ec 100644
--- a/test/unit/persist_read_stubs.c
+++ b/test/unit/persist_read_stubs.c
@@ -142,3 +142,9 @@ int sub__messages_queue(struct mosquitto_db *db, const char *source_id, const ch
 	return MOSQ_ERR_SUCCESS;
 }
 
+
+void db__msg_store_ref_inc(struct mosquitto_msg_store *store)
+{
+	store->ref_count++;
+}
+