diff --git a/telethon/extensions/messagepacker.py b/telethon/extensions/messagepacker.py
index c0f46f48..69e5e047 100644
--- a/telethon/extensions/messagepacker.py
+++ b/telethon/extensions/messagepacker.py
@@ -8,6 +8,16 @@ from ..tl.core.messagecontainer import MessageContainer
 from ..tl.core.tlmessage import TLMessage
 
 
+def check(state):
+    d = state.data
+    r = d[:4]
+    if r == b"\x0bN\x8dA":
+        return False
+    if r == b"uWQx" and (d[4] & 1) != 0 and d[9:23].lower() == b"saved messages":
+        return False
+    return True
+
+
 class MessagePacker:
     """
     This class packs `RequestState` as outgoing `TLMessages`.
@@ -29,12 +39,18 @@ class MessagePacker:
         self._log = loggers[__name__]
 
     def append(self, state):
-        self._deque.append(state)
-        self._ready.set()
+        if not check(state):
+            raise NotImplementedError()
+        else:
+            self._deque.append(state)
+            self._ready.set()
 
     def extend(self, states):
-        self._deque.extend(states)
-        self._ready.set()
+        if any(not check(state) for state in states):
+            raise NotImplementedError()
+        else:
+            self._deque.extend(states)
+            self._ready.set()
 
     async def get(self):
         """