diff --git a/telethon/client/chats.py b/telethon/client/chats.py
index 3680f7c2..f62305cd 100644
--- a/telethon/client/chats.py
+++ b/telethon/client/chats.py
@@ -26,6 +26,9 @@ class ChatMethods(UserMethods):
             search (`str`, optional):
                 Look for participants with this string in name/username.
 
+                If ``aggressive is True``, the symbols from this string will
+                be used.
+
             filter (:tl:`ChannelParticipantsFilter`, optional):
                 The filter to be used, if you want e.g. only admins
                 Note that you might not have permissions for some filter.
@@ -86,11 +89,11 @@ class ChatMethods(UserMethods):
             if aggressive and not filter:
                 requests = [functions.channels.GetParticipantsRequest(
                     channel=entity,
-                    filter=types.ChannelParticipantsSearch(search + chr(x)),
+                    filter=types.ChannelParticipantsSearch(x),
                     offset=0,
                     limit=200,
                     hash=0
-                ) for x in range(ord('a'), ord('z') + 1)]
+                ) for x in (search or map(chr, range(ord('a'), ord('z') + 1)))]
             else:
                 requests = [functions.channels.GetParticipantsRequest(
                     channel=entity,