diff --git a/.travis.yml b/.travis.yml
index a08241f..339b667 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,6 +17,7 @@ install:
   - pip install aiorpcX
   - pip install ecdsa
   - pip install plyvel
+  - pip install pycodestyle
   - pip install pyrocksdb
   - pip install tribus-hash
   - pip install pytest-cov
@@ -25,7 +26,9 @@ install:
   - pip install x11_hash
   - pip install xevan_hash
 # command to run tests
-script: pytest --cov=server --cov=lib --cov=wallet
+script:
+  - pytest --cov=server --cov=lib --cov=wallet
+  - pycodestyle server/*.py
 # Dont report coverage from nightly
 after_success:
   - if [[ $(python3 -V 2>&1) == *"Python 3.6"* ]]; then
diff --git a/server/controller.py b/server/controller.py
index 351e777..5d23fa0 100644
--- a/server/controller.py
+++ b/server/controller.py
@@ -87,8 +87,8 @@ class Controller(ServerBase):
         self.mn_cache = pylru.lrucache(256)
         env.max_send = max(350000, env.max_send)
         # Set up the RPC request handlers
-        cmds = ('add_peer daemon_url disconnect getinfo groups log peers reorg '
-                'sessions stop'.split())
+        cmds = ('add_peer daemon_url disconnect getinfo groups log peers '
+                'reorg sessions stop'.split())
         self.rpc_handlers = {cmd: getattr(self, 'rpc_' + cmd) for cmd in cmds}
 
         self.loop = asyncio.get_event_loop()
diff --git a/server/daemon.py b/server/daemon.py
index 70ccf54..e0e97b3 100644
--- a/server/daemon.py
+++ b/server/daemon.py
@@ -217,8 +217,8 @@ class Daemon(object):
                     # probably because we did not provide arguments
                     available = True
                 else:
-                    self.logger.warning('unexpected error (code {:d}: {}) when '
-                                        'testing RPC availability of method {}'
+                    self.logger.warning('error (code {:d}: {}) when testing '
+                                        'RPC availability of method {}'
                                         .format(error_code, err.get("message"),
                                                 method))
                     available = False
@@ -264,7 +264,8 @@ class Daemon(object):
 
     async def getrawtransaction(self, hex_hash, verbose=False):
         '''Return the serialized raw transaction with the given hash.'''
-        return await self._send_single('getrawtransaction', (hex_hash, int(verbose)))
+        return await self._send_single('getrawtransaction',
+                                       (hex_hash, int(verbose)))
 
     async def getrawtransactions(self, hex_hashes, replace_errs=True):
         '''Return the serialized raw transactions with the given hashes.
@@ -305,7 +306,7 @@ class DashDaemon(Daemon):
         '''Broadcast a transaction to the network.'''
         return await self._send_single('masternodebroadcast', params)
 
-    async def masternode_list(self, params ):
+    async def masternode_list(self, params):
         '''Return the masternode status.'''
         return await self._send_single('masternodelist', params)
 
@@ -350,13 +351,14 @@ class LegacyRPCDaemon(Daemon):
         pbh = b.get('previousblockhash')
         if pbh is None:
             pbh = '0' * 64
-        header = pack('<L', b.get('version')) \
-                 + hex_str_to_hash(pbh) \
-                 + hex_str_to_hash(b.get('merkleroot')) \
-                 + pack('<L', self.timestamp_safe(b['time'])) \
-                 + pack('<L', int(b.get('bits'), 16)) \
-                 + pack('<L', int(b.get('nonce')))
-        return header
+        return b''.join([
+            pack('<L', b.get('version')),
+            hex_str_to_hash(pbh),
+            hex_str_to_hash(b.get('merkleroot')),
+            pack('<L', self.timestamp_safe(b['time'])),
+            pack('<L', int(b.get('bits'), 16)),
+            pack('<L', int(b.get('nonce')))
+        ])
 
     async def make_raw_block(self, b):
         '''Construct a raw block'''
diff --git a/server/env.py b/server/env.py
index 99293f8..add8f19 100644
--- a/server/env.py
+++ b/server/env.py
@@ -132,8 +132,10 @@ class Env(EnvBase):
                 result = getattr(clearnet, port_kind)
             return result or getattr(self, port_kind)
 
-        tcp_port = self.integer('REPORT_TCP_PORT_TOR', port('tcp_port')) or None
-        ssl_port = self.integer('REPORT_SSL_PORT_TOR', port('ssl_port')) or None
+        tcp_port = self.integer('REPORT_TCP_PORT_TOR',
+                                port('tcp_port')) or None
+        ssl_port = self.integer('REPORT_SSL_PORT_TOR',
+                                port('ssl_port')) or None
         if tcp_port == ssl_port:
             raise self.Error('REPORT_TCP_PORT_TOR and REPORT_SSL_PORT_TOR '
                              'both resolve to {}'.format(tcp_port))
diff --git a/server/mempool.py b/server/mempool.py
index 535b683..fca79bf 100644
--- a/server/mempool.py
+++ b/server/mempool.py
@@ -176,7 +176,8 @@ class MemPool(object):
                     txin_pairs, txout_pairs, tx_fee, tx_size = item
                     fee_rate = tx_fee // tx_size
                     fee_hist[fee_rate] += tx_size
-                    for hashX, value in itertools.chain(txin_pairs, txout_pairs):
+                    for hashX, value in itertools.chain(txin_pairs,
+                                                        txout_pairs):
                         touched.add(hashX)
                         hashXs[hashX].add(hex_hash)
 
@@ -380,12 +381,12 @@ class MemPool(object):
         # [fee_(n-1), fee_n)], and fee_(n-1) > fee_n. Fee intervals
         # are chosen so as to create tranches that contain at least
         # 100kb of transactions
-        l = list(reversed(sorted(self.fee_histogram.items())))
+        items = list(reversed(sorted(self.fee_histogram.items())))
         out = []
         size = 0
         r = 0
         binsize = 100000
-        for fee, s in l:
+        for fee, s in items:
             size += s
             if size + r > binsize:
                 out.append((fee, size))
diff --git a/server/peers.py b/server/peers.py
index aa16b05..d7062c4 100644
--- a/server/peers.py
+++ b/server/peers.py
@@ -232,8 +232,8 @@ class PeerManager(object):
         self.loop = controller.loop
 
         # Our clearnet and Tor Peers, if any
-        self.myselves =  [Peer(ident.host, controller.server_features(), 'env')
-                          for ident in env.identities]
+        self.myselves = [Peer(ident.host, controller.server_features(), 'env')
+                         for ident in env.identities]
         self.retry_event = asyncio.Event()
         # Peers have one entry per hostname.  Once connected, the
         # ip_addr property is either None, an onion peer, or the
diff --git a/server/session.py b/server/session.py
index e8db1e0..d3fac0c 100644
--- a/server/session.py
+++ b/server/session.py
@@ -294,7 +294,7 @@ class ElectrumX(SessionBase):
         start_height = self.controller.non_negative_integer(start_height)
         count = self.controller.non_negative_integer(count)
         count = min(count, self.MAX_CHUNK_SIZE)
-        hex_str, n =  self.controller.block_headers(start_height, count)
+        hex_str, n = self.controller.block_headers(start_height, count)
         return {'hex': hex_str, 'count': n, 'max': self.MAX_CHUNK_SIZE}
 
     def block_get_chunk(self, index):
@@ -304,7 +304,7 @@ class ElectrumX(SessionBase):
         index = self.controller.non_negative_integer(index)
         chunk_size = self.controller.coin.CHUNK_SIZE
         start_height = index * chunk_size
-        hex_str, n =  self.controller.block_headers(start_height, chunk_size)
+        hex_str, n = self.controller.block_headers(start_height, chunk_size)
         return hex_str
 
     def is_tor(self):
@@ -503,7 +503,7 @@ class DashElectrumX(ElectrumX):
         for masternode in self.mns:
             status = await self.daemon.masternode_list(['status', masternode])
             self.send_notification('masternode.subscribe',
-                                    [masternode, status.get(masternode)])
+                                   [masternode, status.get(masternode)])
 
     def notify(self, height, touched):
         '''Notify the client about changes in masternode list.'''
@@ -511,7 +511,6 @@ class DashElectrumX(ElectrumX):
         self.controller.create_task(self.notify_masternodes_async())
         return result
 
-
     # Masternode command handlers
     async def masternode_announce_broadcast(self, signmnb):
         '''Pass through the masternode announce message to be broadcast
@@ -553,7 +552,7 @@ class DashElectrumX(ElectrumX):
             mns: a list of masternodes information.
             '''
             now = int(datetime.datetime.utcnow().strftime("%s"))
-            mn_queue=[]
+            mn_queue = []
 
             # Only ENABLED masternodes are considered for the list.
             for line in mns:
@@ -590,9 +589,11 @@ class DashElectrumX(ElectrumX):
                     break
             return position
 
-        # Accordingly with the masternode payment queue, a custom list with
-        # the masternode information including the payment position is returned.
-        if self.controller.cache_mn_height != self.height() or not self.controller.mn_cache:
+        # Accordingly with the masternode payment queue, a custom list
+        # with the masternode information including the payment
+        # position is returned.
+        if (self.controller.cache_mn_height != self.height()
+                or not self.controller.mn_cache):
             self.controller.cache_mn_height = self.height()
             self.controller.mn_cache.clear()
             full_mn_list = await self.daemon.masternode_list(['full'])
@@ -611,17 +612,21 @@ class DashElectrumX(ElectrumX):
                 mn_info['lastpaidtime'] = mn_data[5]
                 mn_info['lastpaidblock'] = mn_data[6]
                 mn_info['ip'] = mn_data[7]
-                mn_info['paymentposition'] = get_payment_position(mn_payment_queue, mn_info['payee'])
-                mn_info['inselection'] = mn_info['paymentposition'] < mn_payment_count // 10
-                balance = await self.controller.address_get_balance(mn_info['payee'])
-                mn_info['balance'] = sum(balance.values()) / self.controller.coin.VALUE_PER_COIN
+                mn_info['paymentposition'] = get_payment_position(
+                    mn_payment_queue, mn_info['payee'])
+                mn_info['inselection'] = (
+                    mn_info['paymentposition'] < mn_payment_count // 10)
+                balance = await self.controller.address_get_balance(
+                    mn_info['payee'])
+                mn_info['balance'] = (sum(balance.values())
+                                      / self.controller.coin.VALUE_PER_COIN)
                 mn_list.append(mn_info)
             self.controller.mn_cache = mn_list
 
         # If payees is an empty list the whole masternode list is returned
         if payees:
             result = [mn for mn in self.controller.mn_cache
-            for address in payees if mn['payee'] == address]
+                      for address in payees if mn['payee'] == address]
         else:
             result = self.controller.mn_cache