diff --git a/telethon/client/telegrambaseclient.py b/telethon/client/telegrambaseclient.py
index 3c2ec9df..662d5733 100644
--- a/telethon/client/telegrambaseclient.py
+++ b/telethon/client/telegrambaseclient.py
@@ -1,4 +1,5 @@
 import abc
+import inspect
 import re
 import asyncio
 import collections
@@ -319,6 +320,9 @@ class TelegramBaseClient(abc.ABC):
         self.api_id = int(api_id)
         self.api_hash = api_hash
 
+        if inspect.iscoroutinefunction(self.session.process_entities):
+            self._log[__name__].warning('Using async sessions support is a experimental feature')
+
         # Current proxy implementation requires `sock_connect`, and some
         # event loops lack this method. If the current loop is missing it,
         # bail out early and suggest an alternative.