diff --git a/pyrogram/storage/memory_storage.py b/pyrogram/storage/memory_storage.py
index 49343540..5f097a1c 100644
--- a/pyrogram/storage/memory_storage.py
+++ b/pyrogram/storage/memory_storage.py
@@ -36,7 +36,8 @@ class MemoryStorage(SQLiteStorage):
 
         if self.name != ":memory:":
             dc_id, test_mode, auth_key, user_id, is_bot = struct.unpack(
-                self.SESSION_STRING_FORMAT,
+                (self.SESSION_STRING_FORMAT if len(self.name) == MemoryStorage.SESSION_STRING_SIZE else
+                 self.SESSION_STRING_FORMAT_64),
                 base64.urlsafe_b64decode(
                     self.name + "=" * (-len(self.name) % 4)
                 )
diff --git a/pyrogram/storage/storage.py b/pyrogram/storage/storage.py
index c506c8ca..3690cafd 100644
--- a/pyrogram/storage/storage.py
+++ b/pyrogram/storage/storage.py
@@ -20,10 +20,14 @@ import base64
 import struct
 from typing import List, Tuple
 
+from pyrogram import utils
+
 
 class Storage:
     SESSION_STRING_FORMAT = ">B?256sI?"
+    SESSION_STRING_FORMAT_64 = ">B?256sQ?"
     SESSION_STRING_SIZE = 351
+    SESSION_STRING_SIZE_64 = 356
 
     def __init__(self, name: str):
         self.name = name
@@ -71,13 +75,14 @@ class Storage:
         raise NotImplementedError
 
     async def export_session_string(self):
+        user_id = await self.user_id()
         return base64.urlsafe_b64encode(
             struct.pack(
-                self.SESSION_STRING_FORMAT,
+                self.SESSION_STRING_FORMAT if user_id < utils.MAX_USER_ID_OLD else self.SESSION_STRING_FORMAT_64,
                 await self.dc_id(),
                 await self.test_mode(),
                 await self.auth_key(),
-                await self.user_id(),
+                user_id,
                 await self.is_bot()
             )
         ).decode().rstrip("=")
diff --git a/pyrogram/utils.py b/pyrogram/utils.py
index e5b15aad..9d53d8bf 100644
--- a/pyrogram/utils.py
+++ b/pyrogram/utils.py
@@ -159,6 +159,7 @@ def unpack_inline_message_id(inline_message_id: str) -> "raw.types.InputBotInlin
 MIN_CHANNEL_ID = -1002147483647
 MAX_CHANNEL_ID = -1000000000000
 MIN_CHAT_ID = -2147483647
+MAX_USER_ID_OLD = 2147483647
 MAX_USER_ID = 999999999999