diff --git a/server/db.py b/server/db.py
index 85e2231..3a5dae7 100644
--- a/server/db.py
+++ b/server/db.py
@@ -128,9 +128,7 @@ class UTXOCache(object):
             #    self.logger.info('duplicate tx hash {}'
             #                     .format(bytes(reversed(tx_hash)).hex()))
 
-            # b''.join avoids this: https://bugs.python.org/issue13298
-            self.cache[key] = b''.join(
-                (hash168, tx_numb, pack('<Q', txout.value)))
+            self.cache[key] = hash168 + tx_numb + pack('<Q', txout.value)
 
         return hash168s
 
@@ -141,7 +139,7 @@ class UTXOCache(object):
         '''
         # Fast track is it's in the cache
         pack = struct.pack
-        key = b''.join((prevout.hash, pack('<H', prevout.n)))
+        key = prevout.hash + pack('<H', prevout.n)
         value = self.cache.pop(key, None)
         if value:
             self.cache_hits += 1
diff --git a/server/server.py b/server/server.py
index 9eeb4a3..22f7610 100644
--- a/server/server.py
+++ b/server/server.py
@@ -136,7 +136,7 @@ class BlockCache(object):
             blocks = await self.send_vector('getblock', param_lists)
             self.fetched_height += count
 
-            # Convert hex string to bytes and put in memoryview
+            # Convert hex string to bytes
             blocks = [bytes.fromhex(block) for block in blocks]
             # Reverse order and place at front of list
             self.blocks = list(reversed(blocks)) + self.blocks