diff --git a/telethon/tl/tlobject.py b/telethon/tl/tlobject.py
index 67a86300..1bd57878 100644
--- a/telethon/tl/tlobject.py
+++ b/telethon/tl/tlobject.py
@@ -93,8 +93,11 @@ class TLObject:
     @staticmethod
     def serialize_bytes(data):
         """Write bytes by using Telegram guidelines"""
-        if isinstance(data, str):
-            data = data.encode('utf-8')
+        if not isinstance(data, bytes):
+            if isinstance(data, str):
+                data = data.encode('utf-8')
+            else:
+                raise ValueError('bytes or str expected, not', type(data))
 
         r = []
         if len(data) < 254:
diff --git a/telethon/update_state.py b/telethon/update_state.py
index 8dd2ffad..9410125e 100644
--- a/telethon/update_state.py
+++ b/telethon/update_state.py
@@ -119,10 +119,10 @@ class UpdateState:
                         handler(update)
             except StopIteration:
                 break
-            except Exception as e:
+            except:
                 # We don't want to crash a worker thread due to any reason
-                self._logger.debug(
-                    '[ERROR] Unhandled exception on worker {}'.format(wid), e
+                self._logger.exception(
+                    '[ERROR] Unhandled exception on worker {}'.format(wid)
                 )
 
     def process(self, update):
diff --git a/telethon_generator/__init__.py b/telethon_generator/__init__.py
new file mode 100644
index 00000000..8b137891
--- /dev/null
+++ b/telethon_generator/__init__.py
@@ -0,0 +1 @@
+
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