diff --git a/tests/base.py b/tests/base.py
index cd8c0c7802..4a4e536a33 100644
--- a/tests/base.py
+++ b/tests/base.py
@@ -638,8 +638,11 @@ class FakeGerritChange(object):
 
         path = os.path.join(self.upstream_root, self.project)
         repo = git.Repo(path)
-        repo.heads[self.branch].commit = \
-            repo.commit(self.patchsets[-1]['revision'])
+
+        repo.head.reference = self.branch
+        zuul.merger.merger.reset_repo_to_head(repo)
+        repo.git.merge('-s', 'resolve', self.patchsets[-1]['ref'])
+        repo.heads[self.branch].commit = repo.head.commit
 
     def setReported(self):
         self.reported += 1
diff --git a/tests/fixtures/config/zuultrigger/project-change-merged/git/common-config/zuul.yaml b/tests/fixtures/config/zuultrigger/project-change-merged/git/common-config/zuul.yaml
index 045e0a9887..77a96c25b8 100644
--- a/tests/fixtures/config/zuultrigger/project-change-merged/git/common-config/zuul.yaml
+++ b/tests/fixtures/config/zuultrigger/project-change-merged/git/common-config/zuul.yaml
@@ -36,6 +36,10 @@
     name: merge-check
     manager: independent
     ignore-dependencies: true
+    reject:
+      gerrit:
+        approval:
+          - Verified: -1
     trigger:
       zuul:
         - event: project-change-merged
diff --git a/tests/unit/test_serial.py b/tests/unit/test_serial.py
index 458d860dbd..f91bb4eda0 100644
--- a/tests/unit/test_serial.py
+++ b/tests/unit/test_serial.py
@@ -26,14 +26,7 @@ class TestSerial(ZuulTestCase):
         A.setMerged()
         self.fake_gerrit.addEvent(A.getChangeMergedEvent())
         self.waitUntilSettled()
-        # The gerrit upstream repo simulation isn't perfect -- when
-        # change A is merged above, the master ref is updated to point
-        # to that change, it doesn't actually "merge" it.  The same is
-        # true for B, so if it didn't have A in its git history, then
-        # A would not appear in the jobs run for B.  We simulate the
-        # correct situation by setting A as the git parent of B.
-        B = self.fake_gerrit.addFakeChange('org/project', 'master', 'B',
-                                           parent='refs/changes/1/1/1')
+        B = self.fake_gerrit.addFakeChange('org/project', 'master', 'B')
         B.setMerged()
         self.fake_gerrit.addEvent(B.getChangeMergedEvent())
         self.waitUntilSettled()
diff --git a/tests/unit/test_zuultrigger.py b/tests/unit/test_zuultrigger.py
index 80cb7387cc..aeda124332 100644
--- a/tests/unit/test_zuultrigger.py
+++ b/tests/unit/test_zuultrigger.py
@@ -220,6 +220,12 @@ class TestZuulTriggerProjectChangeMerged(ZuulTestCase):
         self.assertTrue("project:{org/project} status:open" in
                         self.fake_gerrit.queries)
 
+        # Ensure the gerrit driver has updated its cache after the
+        # previous comments were left:
+        self.fake_gerrit.addEvent(A.getChangeCommentEvent(2))
+        self.fake_gerrit.addEvent(B.getChangeCommentEvent(2))
+        self.waitUntilSettled()
+
         # Reconfigure and run the test again.  This is a regression
         # check to make sure that we don't end up with a stale trigger
         # cache that has references to projects from the old