diff --git a/README.rst b/README.rst
index 6b32929..ccd46e0 100644
--- a/README.rst
+++ b/README.rst
@@ -113,10 +113,8 @@ be necessary.
 Roadmap Pre-1.0
 ===============
 
-- minor code cleanups
-- at most 1 more DB format change; I will make a weak attempt to
-  retain 0.6 release's DB format if possible
-- provision of bandwidth limit controls
+- minor code cleanups.  It is unlikely DB format will change
+- better DoS protections and mempool handling
 - implement simple protocol to discover peers without resorting to IRC
 
 
diff --git a/RELEASE-NOTES b/RELEASE-NOTES
index 6140ddc..78c83b1 100644
--- a/RELEASE-NOTES
+++ b/RELEASE-NOTES
@@ -1,3 +1,8 @@
+version 0.8.4
+-------------
+
+- remove invalidated histories from cache on new block
+
 version 0.8.3
 -------------
 
diff --git a/electrumx_rpc.py b/electrumx_rpc.py
index 47cb8f6..4535000 100755
--- a/electrumx_rpc.py
+++ b/electrumx_rpc.py
@@ -58,7 +58,7 @@ def main():
     args = parser.parse_args()
 
     if args.port is None:
-        args.port = int(environ.get('ELECTRUMX_RPC_PORT', 8000))
+        args.port = int(environ.get('RPC_PORT', 8000))
 
     loop = asyncio.get_event_loop()
     coro = loop.create_connection(RPCClient, 'localhost', args.port)
diff --git a/lib/jsonrpc.py b/lib/jsonrpc.py
index 861b565..d3d7390 100644
--- a/lib/jsonrpc.py
+++ b/lib/jsonrpc.py
@@ -145,7 +145,7 @@ class JSONRPC(asyncio.Protocol, LoggedClass):
         self.recv_size += len(data)
         self.using_bandwidth(len(data))
 
-        # Close abuvsive connections where buffered data exceeds limit
+        # Close abusive connections where buffered data exceeds limit
         buffer_size = len(data) + sum(len(part) for part in self.parts)
         if buffer_size > self.max_buffer_size:
             self.log_error('read buffer of {:,d} bytes exceeds {:,d} '
diff --git a/server/protocol.py b/server/protocol.py
index 6696c52..70d5014 100644
--- a/server/protocol.py
+++ b/server/protocol.py
@@ -15,7 +15,7 @@ import ssl
 import time
 import traceback
 from collections import defaultdict, namedtuple
-from functools import partial, lru_cache
+from functools import partial
 
 import pylru
 
@@ -231,7 +231,7 @@ class ServerManager(util.LoggedClass):
         self.max_subs = env.max_subs
         self.subscription_count = 0
         self.next_stale_check = 0
-        self.history_cache = pylru.lrucache(512)
+        self.history_cache = pylru.lrucache(128)
         self.futures = []
         env.max_send = max(350000, env.max_send)
         self.logger.info('session timeout: {:,d} seconds'
@@ -318,6 +318,10 @@ class ServerManager(util.LoggedClass):
 
     def notify(self, touched):
         '''Notify sessions about height changes and touched addresses.'''
+        # Remove invalidated history cache
+        hc = self.history_cache
+        for hash168 in set(hc).intersection(touched):
+            del hc[hash168]
         cache = {}
         for session in self.sessions:
             if isinstance(session, ElectrumX):
@@ -537,8 +541,8 @@ class Session(JSONRPC):
     '''Base class of ElectrumX JSON session protocols.
 
     Each session runs its tasks in asynchronous parallelism with other
-    sessions.  To prevent some sessions blocking othersr, potentially
-    long-running requests should yield (not yet implemented).
+    sessions.  To prevent some sessions blocking others, potentially
+    long-running requests should yield.
     '''
 
     def __init__(self, manager, bp, env, kind):
diff --git a/server/version.py b/server/version.py
index 5e72ebe..23e3031 100644
--- a/server/version.py
+++ b/server/version.py
@@ -1 +1 @@
-VERSION = "ElectrumX 0.8.3"
+VERSION = "ElectrumX 0.8.4"