diff --git a/telethon/events/messageedited.py b/telethon/events/messageedited.py
index 3694251f..6a8138a0 100644
--- a/telethon/events/messageedited.py
+++ b/telethon/events/messageedited.py
@@ -7,6 +7,28 @@ from ..tl import types
 class MessageEdited(NewMessage):
     """
     Event fired when a message has been edited.
+
+    .. warning::
+
+        On channels, `Message.out <telethon.tl.custom.message.Message>`
+        will be ``True`` if you sent the message originally, **not if
+        you edited it**! This can be dangerous if you run outgoing
+        commands on edits.
+
+        Some examples follow:
+
+        * You send a message "A", ``out is True``.
+        * You edit "A" to "B", ``out is True``.
+        * Someone else edits "B" to "C", ``out is True`` (**be careful!**).
+        * Someone sends "X", ``out is False``.
+        * Someone edits "X" to "Y", ``out is False``.
+        * You edit "Y" to "Z", ``out is False``.
+
+        Since there are useful cases where you need the right ``out``
+        value, the library cannot do anything automatically to help you.
+        Instead, consider using ``from_users='me'`` (it won't work in
+        broadcast channels at all since the sender is the channel and
+        not you).
     """
     @classmethod
     def build(cls, update):