diff --git a/telethon/network/mtprotosender.py b/telethon/network/mtprotosender.py
index 4bc54d39..6a4970f3 100644
--- a/telethon/network/mtprotosender.py
+++ b/telethon/network/mtprotosender.py
@@ -158,10 +158,10 @@ class MTProtoSender:
             self._recv_loop_handle.cancel()
 
         __log__.info('Disconnection from {} complete!'.format(self._ip))
-        if error is not None:
-            self._connection_dropped.set_result(None)
-        else:
+        if error:
             self._connection_dropped.set_exception(error)
+        else:
+            self._connection_dropped.set_result(None)
 
     def send(self, request, ordered=False):
         """