diff --git a/electrumx/server/chain_state.py b/electrumx/server/chain_state.py
index 8681c1b..38b4e7b 100644
--- a/electrumx/server/chain_state.py
+++ b/electrumx/server/chain_state.py
@@ -7,7 +7,6 @@
 
 
 import asyncio
-import pylru
 
 from aiorpcx import run_in_thread
 
@@ -19,24 +18,15 @@ class ChainState(object):
     blocks, transaction history, UTXOs and the mempool.
     '''
 
-    def __init__(self, env, daemon, bp, notifications):
+    def __init__(self, env, daemon, bp):
         self._env = env
         self._daemon = daemon
         self._bp = bp
-        self._history_cache = pylru.lrucache(256)
 
         # External interface pass-throughs for session.py
         self.force_chain_reorg = self._bp.force_chain_reorg
         self.tx_branch_and_root = self._bp.merkle.branch_and_root
         self.read_headers = self._bp.read_headers
-        # Cache maintenance
-        notifications.add_callback(self._notify)
-
-    async def _notify(self, height, touched):
-        # Invalidate our history cache for touched hashXs
-        hc = self._history_cache
-        for hashX in set(hc).intersection(touched):
-            del hc[hashX]
 
     async def broadcast_transaction(self, raw_tx):
         return await self._daemon.sendrawtransaction([raw_tx])
@@ -65,10 +55,7 @@ class ChainState(object):
             limit = self._env.max_send // 97
             return list(self._bp.get_history(hashX, limit=limit))
 
-        hc = self._history_cache
-        if hashX not in hc:
-            hc[hashX] = await run_in_thread(job)
-        return hc[hashX]
+        return await run_in_thread(job)
 
     async def get_utxos(self, hashX):
         '''Get UTXOs asynchronously to reduce latency.'''
diff --git a/electrumx/server/controller.py b/electrumx/server/controller.py
index 051bed2..da07089 100644
--- a/electrumx/server/controller.py
+++ b/electrumx/server/controller.py
@@ -96,7 +96,7 @@ class Controller(ServerBase):
         BlockProcessor = env.coin.BLOCK_PROCESSOR
         bp = BlockProcessor(env, daemon, notifications)
         mempool = MemPool(env.coin, daemon, notifications, bp.lookup_utxos)
-        chain_state = ChainState(env, daemon, bp, notifications)
+        chain_state = ChainState(env, daemon, bp)
         session_mgr = SessionManager(env, chain_state, mempool,
                                      notifications, shutdown_event)
 
diff --git a/electrumx/server/session.py b/electrumx/server/session.py
index 1dc778e..daf97cd 100644
--- a/electrumx/server/session.py
+++ b/electrumx/server/session.py
@@ -13,6 +13,7 @@ import datetime
 import itertools
 import json
 import os
+import pylru
 import ssl
 import time
 from collections import defaultdict
@@ -119,6 +120,8 @@ class SessionManager(object):
         self.state = self.CATCHING_UP
         self.txs_sent = 0
         self.start_time = time.time()
+        self._history_cache = pylru.lrucache(256)
+        self._hc_height = 0
         # Cache some idea of room to avoid recounting on each subscription
         self.subs_room = 0
         # Masternode stuff only for such coins
@@ -442,8 +445,24 @@ class SessionManager(object):
         '''The number of connections that we've sent something to.'''
         return len(self.sessions)
 
+    async def get_history(self, hashX):
+        '''A caching layer.'''
+        hc = self._history_cache
+        if hashX not in hc:
+            hc[hashX] = await self.chain_state.get_history(hashX)
+        return hc[hashX]
+
     async def _notify_sessions(self, height, touched):
         '''Notify sessions about height changes and touched addresses.'''
+        # Invalidate our history cache for touched hashXs
+        if height != self._hc_height:
+            self._hc_height = height
+            hc = self._history_cache
+            hashXs = set(hc).intersection(touched)
+            text = [hash_to_hex_str(hashX) for hashX in hashXs]
+            for hashX in hashXs:
+                del hc[hashX]
+
         async with TaskGroup() as group:
             for session in self.sessions:
                 await group.spawn(session.notify(height, touched))
@@ -755,7 +774,7 @@ class ElectrumX(SessionBase):
         '''
         # Note history is ordered and mempool unordered in electrum-server
         # For mempool, height is -1 if unconfirmed txins, otherwise 0
-        history = await self.chain_state.get_history(hashX)
+        history = await self.session_mgr.get_history(hashX)
         mempool = await self.mempool.transaction_summaries(hashX)
 
         status = ''.join('{}:{:d}:'.format(hash_to_hex_str(tx_hash), height)
@@ -855,7 +874,7 @@ class ElectrumX(SessionBase):
 
     async def confirmed_and_unconfirmed_history(self, hashX):
         # Note history is ordered but unconfirmed is unordered in e-s
-        history = await self.chain_state.get_history(hashX)
+        history = await self.session_mgr.get_history(hashX)
         conf = [{'tx_hash': hash_to_hex_str(tx_hash), 'height': height}
                 for tx_hash, height in history]
         return conf + await self.unconfirmed_history(hashX)