diff --git a/zuul/merger.py b/zuul/merger.py
index ed89ec8..7ad7eed 100644
--- a/zuul/merger.py
+++ b/zuul/merger.py
@@ -149,6 +149,14 @@
         r.recreateRepoObject()
         return r
 
+    def updateRepo(self, project):
+        repo = self.getRepo(project)
+        try:
+            self.log.info("Updating local repository %s", project)
+            repo.update()
+        except:
+            self.log.exception("Unable to update %s", project)
+
     def _mergeChange(self, change, ref, target_ref, mode):
         repo = self.getRepo(change.project)
         try:
diff --git a/zuul/scheduler.py b/zuul/scheduler.py
index b52e97c..2f5795c 100644
--- a/zuul/scheduler.py
+++ b/zuul/scheduler.py
@@ -403,6 +403,15 @@
             self.trigger_event_queue.task_done()
             return
 
+        # Preprocessing for ref-update events
+        if hasattr(event, 'refspec'):
+            # Make sure the local git repo is up-to-date with the remote one.
+            # We better have the new ref before enqueuing the changes.
+            # This is done before enqueuing the changes to avoid calling an
+            # update per pipeline accepting the change.
+            self.log.info("Fetching references for %s" % project)
+            self.merger.updateRepo(project)
+
         for pipeline in self.pipelines.values():
             change = event.getChange(project, self.trigger)
             if event.type == 'patchset-created':