diff --git a/python/samba/tests/kcc/__init__.py b/python/samba/tests/kcc/__init__.py
index 3d33295e575..39167824d35 100644
--- a/python/samba/tests/kcc/__init__.py
+++ b/python/samba/tests/kcc/__init__.py
@@ -75,6 +75,22 @@ class KCCTests(samba.tests.TestCase):
         my_kcc = kcc.KCC(unix_now, readonly=True, verify=True,
                          debug=False, dot_file_dir=None)
 
+        #
+        # The following seems to raise
+        # samba.kcc.graph_utils.GraphError when something
+        # goes wrong.
+        #
+        # Typically failureException is exceptions.AssertionError
+        # by default, see pydoc unittest.TestCase
+        #
+        # As this is flapping under python3, we need to
+        # make sure it generates a failure instead of an error.
+        #
+        # We need to make sure samba.kcc.graph_utils.GraphError
+        # will generate a failure from here on.
+        #
+        self.failureException = samba.kcc.graph_utils.GraphError
+
         my_kcc.run("ldap://%s" % os.environ["SERVER"],
                    self.lp, self.creds,
                    attempt_live_connections=False)