diff --git a/aiohttp/client.py b/aiohttp/client.py
index 6edfe4b8ffc..3c962095dbc 100644
--- a/aiohttp/client.py
+++ b/aiohttp/client.py
@@ -482,6 +482,7 @@ def detach(self):
         self._connector = None
 
     def __enter__(self):
+        warnings.warn("Use async with instead", DeprecationWarning)
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):