diff --git a/telethon/client/telegrambaseclient.py b/telethon/client/telegrambaseclient.py
index 32790334..039e7efc 100644
--- a/telethon/client/telegrambaseclient.py
+++ b/telethon/client/telegrambaseclient.py
@@ -664,7 +664,7 @@ class TelegramBaseClient(abc.ABC):
         ss, cs = self._message_box.session_state()
         self.session.set_update_state(0, types.updates.State(**ss, unread_count=0))
         now = datetime.datetime.now()  # any datetime works; channels don't need it
-        entities_ids = [e.id for e in entities]
+        entities_ids = (e.id for e in entities)
         for channel_id, pts in cs.items():
             if channel_id in entities_ids:
                 self.session.set_update_state(channel_id, types.updates.State(pts, 0, now, 0, unread_count=0))