diff --git a/network/swarm.py b/network/swarm.py
index 41ef9bc..dc1f67e 100644
--- a/network/swarm.py
+++ b/network/swarm.py
@@ -59,9 +59,7 @@ class Swarm(INetwork):
 
         # Use muxed conn to open stream, which returns
         # a muxed stream
-        # TODO: use better stream IDs
-        stream_id = (uuid.uuid4().int & (1<<64)-1) >> 3
-        muxed_stream = muxed_conn.open_stream(protocol_id, stream_id, peer_id, multiaddr)
+        muxed_stream = await muxed_conn.open_stream(protocol_id, peer_id, multiaddr)
 
         # Create a net stream
         net_stream = NetStream(muxed_stream)
diff --git a/stream_muxer/mplex/mplex.py b/stream_muxer/mplex/mplex.py
index 516dce2..2d677d5 100644
--- a/stream_muxer/mplex/mplex.py
+++ b/stream_muxer/mplex/mplex.py
@@ -16,16 +16,24 @@ class Mplex(IMuxedConn):
         """
         self.raw_conn = conn
         self.initiator = initiator
+
+        # Mapping from stream ID -> buffer of messages for that stream
         self.buffers = {}
-        self.streams = {}
+
         self.stream_queue = asyncio.Queue()
         self.conn_lock = asyncio.Lock()
+        self._next_id = 0
 
         # The initiator need not read upon construction time.
         # It should read when the user decides that it wants to read from the constructed stream.
         if not initiator:
             asyncio.ensure_future(self.handle_incoming())
 
+    def _next_stream_id(self):
+        next_id = self._next_id
+        self._next_id += 1
+        return next_id
+
     def close(self):
         """
         close the stream muxer and underlying raw connection
@@ -49,7 +57,7 @@ class Mplex(IMuxedConn):
         self.buffers[stream_id] = bytearray()
         return data
 
-    def open_stream(self, protocol_id, stream_id, peer_id, multi_addr):
+    async def open_stream(self, protocol_id, peer_id, multi_addr):
         """
         creates a new muxed_stream
         :param protocol_id: protocol_id of stream
@@ -58,8 +66,9 @@ class Mplex(IMuxedConn):
         :param multi_addr: multi_addr that stream connects to
         :return: a new stream
         """
+        stream_id = self._next_stream_id()
         stream = MplexStream(stream_id, multi_addr, self)
-        self.streams[stream_id] = stream
+        self.buffers[stream_id] = bytearray()
         return stream
 
     async def accept_stream(self):