diff --git a/java/com/google/gerrit/server/submit/SubscriptionGraph.java b/java/com/google/gerrit/server/submit/SubscriptionGraph.java
index 26c8ac9..dfbbf81 100644
--- a/java/com/google/gerrit/server/submit/SubscriptionGraph.java
+++ b/java/com/google/gerrit/server/submit/SubscriptionGraph.java
@@ -332,6 +332,8 @@
         MergeOpRepoManager orm)
         throws IOException {
       Collection<SubmoduleSubscription> ret = new ArrayList<>();
+      if (RefNames.isGerritRef(srcBranch.branch())) return ret;
+
       Project.NameKey srcProject = srcBranch.project();
       for (SubscribeSection s :
           projectCache