diff --git a/telethon/_updates/__init__.py b/telethon/_updates/__init__.py
index 7da2c047..42afce1d 100644
--- a/telethon/_updates/__init__.py
+++ b/telethon/_updates/__init__.py
@@ -1,2 +1,3 @@
 from .entitycache import EntityCache
 from .messagebox import MessageBox, GapError
+from .session import SessionState, ChannelState, Entity, EntityType
diff --git a/telethon/_updates/session.py b/telethon/_updates/session.py
index 77ec30ae..99577c1d 100644
--- a/telethon/_updates/session.py
+++ b/telethon/_updates/session.py
@@ -1,5 +1,6 @@
 from typing import Optional, Tuple
 from enum import IntEnum
+from ..tl.types import InputPeerUser, InputPeerChat, InputPeerChannel
 
 
 class SessionState:
@@ -175,3 +176,11 @@ class Entity:
 
     def __bytes__(self):
         return struct.pack('<Bqq', self.ty, self.id, self.hash)
+
+    def _as_input_peer(self):
+        if self.is_user:
+            return InputPeerUser(self.id, self.hash)
+        elif self.ty == EntityType.GROUP:
+            return InputPeerChat(self.id)
+        else:
+            return InputPeerChannel(self.id, self.hash)
diff --git a/telethon/client/telegrambaseclient.py b/telethon/client/telegrambaseclient.py
index c0375eab..d7240662 100644
--- a/telethon/client/telegrambaseclient.py
+++ b/telethon/client/telegrambaseclient.py
@@ -15,7 +15,7 @@ from ..network import MTProtoSender, Connection, ConnectionTcpFull, TcpMTProxy
 from ..sessions import Session, SQLiteSession, MemorySession
 from ..tl import functions, types
 from ..tl.alltlobjects import LAYER
-from .._updates import MessageBox, EntityCache as MbEntityCache
+from .._updates import MessageBox, EntityCache as MbEntityCache, SessionState, ChannelState, Entity, EntityType
 
 DEFAULT_DC_ID = 2
 DEFAULT_IPV4_IP = '149.154.167.51'
@@ -535,6 +535,23 @@ class TelegramBaseClient(abc.ABC):
         self.session.auth_key = self._sender.auth_key
         await self.session.save()
 
+        if self._catch_up:
+            ss = SessionState(0, 0, False, 0, 0, 0, 0, None)
+            cs = []
+
+            for entity_id, state in await self.session.get_update_states():
+                if entity_id == 0:
+                    # TODO current session doesn't store self-user info but adding that is breaking on downstream session impls
+                    ss = SessionState(0, 0, False, state.pts, state.qts, state.date, state.seq, None)
+                else:
+                    cs.append(ChannelState(entity_id, state.pts))
+
+            self._message_box.load(ss, cs)
+            for state in cs:
+                entity = await self.session.get_input_entity(state.channel_id)
+                if entity:
+                    self._mb_entity_cache.put(Entity(EntityType.CHANNEL, entity.channel_id, entity.access_hash))
+
         self._init_request.query = functions.help.GetConfigRequest()
 
         await self._sender.send(functions.InvokeWithLayerRequest(
@@ -642,6 +659,17 @@ class TelegramBaseClient(abc.ABC):
             await asyncio.wait(self._event_handler_tasks)
             self._event_handler_tasks.clear()
 
+        entities = self._entity_cache.get_all_entities()
+
+        # Piggy-back on an arbitrary TL type with users and chats so the session can understand to read the entities.
+        # It doesn't matter if we put users in the list of chats.
+        await self.session.process_entities(types.contacts.ResolvedPeer(None, [e._as_input_peer() for e in entities], []))
+
+        session_state, channel_states = self._message_box.session_state()
+        await self.session.set_update_state(0, types.updates.State(ss.pts, ss.qts, ss.date, ss.seq, unread_count=0))
+        for channel_id, pts in channel_states.items():
+            await self.session.set_update_state(channel_id, types.updates.State(pts, 0, None, 0, unread_count=0))
+
         await self.session.close()
 
     async def _disconnect(self: 'TelegramClient'):
diff --git a/telethon/client/updates.py b/telethon/client/updates.py
index c100bef3..4ba76b9c 100644
--- a/telethon/client/updates.py
+++ b/telethon/client/updates.py
@@ -266,7 +266,7 @@ class UpdateMethods:
                     self._log[__name__].info('Getting difference for account updates')
                     diff = await self(get_diff)
                     updates, users, chats = self._message_box.apply_difference(diff, self._mb_entity_cache)
-                    updates_to_dispatch.extend(await self._preprocess_updates(updates, users, chats))
+                    updates_to_dispatch.extend(self._preprocess_updates(updates, users, chats))
                     continue
 
                 get_diff = self._message_box.get_channel_difference(self._mb_entity_cache)
@@ -274,7 +274,7 @@ class UpdateMethods:
                     self._log[__name__].info('Getting difference for channel updates')
                     diff = await self(get_diff)
                     updates, users, chats = self._message_box.apply_channel_difference(get_diff, diff, self._mb_entity_cache)
-                    updates_to_dispatch.extend(await self._preprocess_updates(updates, users, chats))
+                    updates_to_dispatch.extend(self._preprocess_updates(updates, users, chats))
                     continue
 
                 deadline = self._message_box.check_deadlines()
@@ -293,14 +293,11 @@ class UpdateMethods:
                 except GapError:
                     continue  # get(_channel)_difference will start returning requests
 
-                updates_to_dispatch.extend(await self._preprocess_updates(processed, users, chats))
+                updates_to_dispatch.extend(self._preprocess_updates(processed, users, chats))
         except Exception:
             self._log[__name__].exception('Fatal error handling updates (this is a bug in Telethon, please report it)')
 
-    async def _preprocess_updates(self, updates, users, chats):
-        await self.session.process_entities(update)
-        self._entity_cache.add(update)
-
+    def _preprocess_updates(self, updates, users, chats):
         self._mb_entity_cache.extend(users, chats)
         entities = {utils.get_peer_id(x): x
                     for x in itertools.chain(users, chats)}
diff --git a/telethon/sessions/abstract.py b/telethon/sessions/abstract.py
index 94afac86..75dcdd00 100644
--- a/telethon/sessions/abstract.py
+++ b/telethon/sessions/abstract.py
@@ -97,6 +97,12 @@ class Session(ABC):
         """
         raise NotImplementedError
 
+    @abstractmethod
+    async def get_update_states(self):
+        """
+        Returns an iterable over all known pairs of ``(entity ID, update state)``.
+        """
+
     @abstractmethod
     async def close(self):
         """
diff --git a/telethon/sessions/memory.py b/telethon/sessions/memory.py
index 8494545c..2f8e1ad6 100644
--- a/telethon/sessions/memory.py
+++ b/telethon/sessions/memory.py
@@ -77,6 +77,9 @@ class MemorySession(Session):
     async def set_update_state(self, entity_id, state):
         self._update_states[entity_id] = state
 
+    async def get_update_states(self):
+        return self._update_states.items()
+
     async def close(self):
         pass
 
diff --git a/telethon/sessions/sqlite.py b/telethon/sessions/sqlite.py
index 26ed586b..2657f835 100644
--- a/telethon/sessions/sqlite.py
+++ b/telethon/sessions/sqlite.py
@@ -215,6 +215,14 @@ class SQLiteSession(MemorySession):
                       entity_id, state.pts, state.qts,
                       state.date.timestamp(), state.seq)
 
+    async def get_update_states(self):
+        c = self._cursor()
+        try:
+            rows = c.execute('select id, pts, qts, date, seq from update_state').fetchall()
+            return ((row[0], types.updates.State(*row[1:], unread_count=0)) for row in rows)
+        finally:
+            c.close()
+
     async def save(self):
         """Saves the current session object as session_user_id.session"""
         # This is a no-op if there are no changes to commit, so there's