diff --git a/aiohttp/web.py b/aiohttp/web.py
index ba68d348bf7..26bd5eaa6ce 100644
--- a/aiohttp/web.py
+++ b/aiohttp/web.py
@@ -301,8 +301,9 @@ async def _handle(self, request):
             ("Handler {!r} should return response instance, "
              "got {!r} [middlewares {!r}]").format(
                  match_info.handler, type(resp),
-                 [middleware for middleware in app.middlewares
-                  for app in match_info.apps])
+                 [middleware
+                  for app in match_info.apps
+                  for middleware in app.middlewares])
         return resp
 
     def __call__(self):