diff --git a/telethon/client/users.py b/telethon/client/users.py
index ddba8ea9..49592494 100644
--- a/telethon/client/users.py
+++ b/telethon/client/users.py
@@ -92,6 +92,8 @@ class UserMethods:
                 self._flood_waited_requests\
                     [request.CONSTRUCTOR_ID] = time.time() + e.seconds
 
+                # In test servers, FLOOD_WAIT_0 has been observed, and sleeping for
+                # such a short amount will cause retries very fast leading to issues.
                 if e.seconds == 0:
                     e.seconds = 1