diff --git a/sprockets_postgres.py b/sprockets_postgres.py
index 48586f2..126f4f8 100644
--- a/sprockets_postgres.py
+++ b/sprockets_postgres.py
@@ -373,7 +373,10 @@ class ApplicationMixin:
                                     _attempt + 1) as connector:
                                 yield connector
                             return
-            exc = on_error('postgres_connector', ConnectionException(str(err)))
+            if on_error is None:
+                raise ConnectionException(str(err))
+            exc = on_error(
+                'postgres_connector', ConnectionException(str(err)))
             if exc:
                 raise exc
             else:  # postgres_status.on_error does not return an exception
diff --git a/tests.py b/tests.py
index c4bdb8a..56b6152 100644
--- a/tests.py
+++ b/tests.py
@@ -168,6 +168,18 @@ class NoErrorRequestHandler(ErrorRequestHandler):
         return None
 
 
+class NoMixinRequestHandler(web.RequestHandler):
+
+    async def get(self):
+        try:
+            async with self.application.postgres_connector() as connector:
+                await connector.execute('SELECT 1', {})
+        except sprockets_postgres.ConnectionException:
+            raise web.HTTPError(503)
+        else:
+            raise web.HTTPError(418)
+
+
 class NoRowRequestHandler(RequestHandler):
 
     GET_SQL = """\
@@ -257,7 +269,7 @@ class UnhandledExceptionRequestHandler(RequestHandler):
             await self.postgres_execute(self.GET_SQL)
         except psycopg2.DataError:
             raise web.HTTPError(422)
-        raise web.HTTPError(500, 'This should have failed')
+        raise web.HTTPError(418, 'This should have failed')
 
     def on_postgres_error(self,
                           metric_name: str,
@@ -271,6 +283,14 @@ class UnhandledExceptionRequestHandler(RequestHandler):
         return exc
 
 
+class DontRaiseRequestHandler(UnhandledExceptionRequestHandler):
+
+    def on_postgres_error(self,
+                          metric_name: str,
+                          exc: Exception) -> typing.Optional[Exception]:
+        return None
+
+
 class Application(sprockets_postgres.ApplicationMixin,
                   app.Application):
 
@@ -303,6 +323,7 @@ class TestCase(testing.SprocketsHttpTestCase):
         self.app = Application(handlers=[
             web.url('/callproc', CallprocRequestHandler),
             web.url('/count', CountRequestHandler),
+            web.url('/dont-raise', DontRaiseRequestHandler),
             web.url('/error', ErrorRequestHandler),
             web.url('/error-passthrough', ErrorPassthroughRequestHandler),
             web.url('/execute', ExecuteRequestHandler),
@@ -310,6 +331,7 @@ class TestCase(testing.SprocketsHttpTestCase):
             web.url('/metrics-mixin', MetricsMixinRequestHandler),
             web.url('/multi-row', MultiRowRequestHandler),
             web.url('/no-error', NoErrorRequestHandler),
+            web.url('/no-mixin', NoMixinRequestHandler),
             web.url('/no-row', NoRowRequestHandler),
             web.url('/pdexecute', ProblemDetailsExecuteRequestHandler),
             web.url('/row-count-no-rows', RowCountNoRowsRequestHandler),
@@ -529,7 +551,7 @@ class RequestHandlerMixinTestCase(TestCase):
         self.assertIsNone(json.loads(response.body)['value'])
 
 
-class RequestHandlerMixinHTTPErrorTestCase(TestCase):
+class HTTPErrorTestCase(TestCase):
 
     def setUp(self):
         super().setUp()
@@ -574,6 +596,25 @@ class RequestHandlerMixinHTTPErrorTestCase(TestCase):
         response = self.fetch('/execute?value=1')
         self.assertEqual(response.code, 503)
 
+    def test_on_error_no_exception_branch(self):
+        response = self.fetch('/dont-raise')
+        self.assertEqual(response.code, 418)
+
+
+class NoMixinTestCase(TestCase):
+
+    @mock.patch('aiopg.cursor.Cursor.execute')
+    def test_postgres_cursor_raises(self, execute):
+        execute.side_effect = psycopg2.ProgrammingError()
+        response = self.fetch('/no-mixin')
+        self.assertEqual(response.code, 500)
+
+    @mock.patch('aiopg.pool.Pool.acquire')
+    def test_postgres_status_connect_error(self, acquire):
+        acquire.side_effect = asyncio.TimeoutError()
+        response = self.fetch('/no-mixin')
+        self.assertEqual(response.code, 503)
+
 
 class TransactionTestCase(TestCase):