From 46ba9696aa6f6b98bb2cb0ac4745149b0d3c4cc2 Mon Sep 17 00:00:00 2001
From: Lonami Exo <totufals@hotmail.com>
Date: Fri, 4 Feb 2022 11:46:08 +0100
Subject: [PATCH] Fix add_handler auto-type detection

---
 telethon/_client/updates.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/telethon/_client/updates.py b/telethon/_client/updates.py
index 2477af9c..e308dfab 100644
--- a/telethon/_client/updates.py
+++ b/telethon/_client/updates.py
@@ -56,7 +56,7 @@ def add_event_handler(
 
     if event is None:
         for param in inspect.signature(callback).parameters.values():
-            event = param.annotation
+            event = None if param.annotation is inspect.Signature.empty else param.annotation
             break  # only check the first parameter
 
     if event is None: