diff --git a/telethon/sessions/memory.py b/telethon/sessions/memory.py
index edd662af..09f029ed 100644
--- a/telethon/sessions/memory.py
+++ b/telethon/sessions/memory.py
@@ -202,9 +202,9 @@ class MemorySession(Session):
                 if username and not invite:
                     result = self.get_entity_rows_by_username(username)
                 else:
-                    key = utils.resolve_invite_link(key)[1]
-                    if key:
-                        result = self.get_entity_rows_by_id(key, exact=False)
+                    tup = utils.resolve_invite_link(key)[1]
+                    if tup:
+                        result = self.get_entity_rows_by_id(tup, exact=False)
 
         elif isinstance(key, int):
             result = self.get_entity_rows_by_id(key, exact)