diff --git a/tests/unit/test_web.py b/tests/unit/test_web.py
index 1045127dfd..a34680f84b 100644
--- a/tests/unit/test_web.py
+++ b/tests/unit/test_web.py
@@ -46,13 +46,10 @@ class FakeConfig(object):
         return self.config.get(section, {}).get(option)
 
 
-class BaseTestWeb(ZuulTestCase):
-    tenant_config_file = 'config/single-tenant/main.yaml'
+class BaseWithWeb(ZuulTestCase):
     config_ini_data = {}
 
-    def setUp(self):
-        super(BaseTestWeb, self).setUp()
-
+    def startWebServer(self):
         self.zuul_ini_config = FakeConfig(self.config_ini_data)
         # Start the web server
         self.web = self.useFixture(
@@ -78,15 +75,6 @@ class BaseTestWeb(ZuulTestCase):
         self.base_url = "http://{host}:{port}".format(
             host=self.host, port=self.port)
 
-    def add_base_changes(self):
-        A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A')
-        A.addApproval('Code-Review', 2)
-        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
-        B = self.fake_gerrit.addFakeChange('org/project1', 'master', 'B')
-        B.addApproval('Code-Review', 2)
-        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
-        self.waitUntilSettled()
-
     def get_url(self, url, *args, **kwargs):
         return requests.get(
             urllib.parse.urljoin(self.base_url, url), *args, **kwargs)
@@ -103,6 +91,23 @@ class BaseTestWeb(ZuulTestCase):
         return requests.options(
             urllib.parse.urljoin(self.base_url, url), *args, **kwargs)
 
+
+class BaseTestWeb(BaseWithWeb):
+    tenant_config_file = 'config/single-tenant/main.yaml'
+
+    def setUp(self):
+        super(BaseTestWeb, self).setUp()
+        self.startWebServer()
+
+    def add_base_changes(self):
+        A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A')
+        A.addApproval('Code-Review', 2)
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        B = self.fake_gerrit.addFakeChange('org/project1', 'master', 'B')
+        B.addApproval('Code-Review', 2)
+        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
     def tearDown(self):
         self.executor_server.hold_jobs_in_build = False
         self.executor_server.release()
@@ -1387,6 +1392,22 @@ class TestTenantInfoConfigBroken(BaseTestWeb):
         self.assertEqual(404, resp.status_code)
 
 
+class TestBrokenConfigCache(BaseWithWeb):
+    tenant_config_file = 'config/single-tenant/main.yaml'
+
+    def test_broken_config_cache(self):
+        # Delete the cached config files from ZK to simulate a
+        # scheduler encountering an error in reconfiguration.
+        path = '/zuul/config/cache/review.example.com%2Forg%2Fproject'
+        self.assertIsNotNone(self.zk_client.client.exists(path))
+        self.zk_client.client.delete(path, recursive=True)
+        self.startWebServer()
+        config_errors = self.get_url(
+            "api/tenant/tenant-one/config-errors").json()
+        self.assertIn('Configuration files missing',
+                      config_errors[0]['error'])
+
+
 class TestWebSocketInfo(TestInfo):
 
     config_ini_data = {
diff --git a/zuul/configloader.py b/zuul/configloader.py
index efefd0976c..58650b1daf 100644
--- a/zuul/configloader.py
+++ b/zuul/configloader.py
@@ -1827,8 +1827,12 @@ class TenantParser(object):
                 extra_config_files = abide.getExtraConfigFiles(project.name)
                 extra_config_dirs = abide.getExtraConfigDirs(project.name)
                 if not self.merger:
-                    raise RuntimeError(
-                        "Cannot load config files without a merger client.")
+                    with project_configuration_exceptions(source_context,
+                                                          loading_errors):
+                        raise Exception(
+                            "Configuration files missing from cache. "
+                            "Check Zuul scheduler logs for more information.")
+                    continue
                 ltime = self.zk_client.getCurrentLtime()
                 job = self.merger.getFiles(
                     project.source.connection.connection_name,