diff --git a/telethon_generator/error_descriptions b/telethon_generator/error_descriptions
index f0a14e68..500504d7 100644
--- a/telethon_generator/error_descriptions
+++ b/telethon_generator/error_descriptions
@@ -45,7 +45,7 @@ PHONE_NUMBER_OCCUPIED=The phone number is already in use
 PHONE_NUMBER_UNOCCUPIED=The phone number is not yet being used
 PHOTO_INVALID_DIMENSIONS=The photo dimensions are invalid
 TYPE_CONSTRUCTOR_INVALID=The type constructor is invalid
-USERNAME_INVALID=Unacceptable username. Must match r"[a-zA-Z][\w\d]{4,31}"
+USERNAME_INVALID=Unacceptable username. Must match r"[a-zA-Z][\w\d]{3,30}[a-zA-Z\d]"
 USERNAME_NOT_MODIFIED=The username is not different from the current username
 USERNAME_NOT_OCCUPIED=The username is not in use by anyone else yet
 USERNAME_OCCUPIED=The username is already taken