diff --git a/libp2p/muxers/mplex/coder.nim b/libp2p/muxers/mplex/coder.nim
index a0a240131..bd15ef796 100644
--- a/libp2p/muxers/mplex/coder.nim
+++ b/libp2p/muxers/mplex/coder.nim
@@ -26,6 +26,11 @@ type
     msgType: MessageType
     data: seq[byte]
 
+  InvalidMplexMsgType = object of CatchableError
+
+proc newInvalidMplexMsgType*(): ref InvalidMplexMsgType =
+  newException(InvalidMplexMsgType, "invalid message type")
+
 proc readMplexVarint(conn: Connection): Future[uint64] {.async, gcsafe.} =
   var
     varint: uint
@@ -41,27 +46,31 @@ proc readMplexVarint(conn: Connection): Future[uint64] {.async, gcsafe.} =
         break
     if res != VarintStatus.Success:
       raise newInvalidVarintException()
-    if varint.int > DefaultReadSize:
-      raise newInvalidVarintSizeException()
     return varint
   except LPStreamIncompleteError as exc:
     trace "unable to read varint", exc = exc.msg
     raise exc
 
 proc readMsg*(conn: Connection): Future[Msg] {.async, gcsafe.} =
-  let headerVarint = await conn.readMplexVarint()
-  trace "read header varint", varint = headerVarint
+  let header = await conn.readMplexVarint()
+  trace "read header varint", varint = header
 
   let dataLenVarint = await conn.readMplexVarint()
   trace "read data len varint", varint = dataLenVarint
 
+  if dataLenVarint.int > DefaultReadSize:
+    raise newInvalidVarintSizeException()
+
   var data: seq[byte] = newSeq[byte](dataLenVarint.int)
   if dataLenVarint.int > 0:
     await conn.readExactly(addr data[0], dataLenVarint.int)
     trace "read data", data = data.len
 
-  let header = headerVarint
-  result = (uint64(header shr 3), MessageType(header and 0x7), data)
+  let msgType = header and 0x7
+  if msgType.int > ord(MessageType.ResetOut):
+    raise newInvalidMplexMsgType()
+
+  result = (uint64(header shr 3), MessageType(msgType), data)
 
 proc writeMsg*(conn: Connection,
                id: uint64,
diff --git a/libp2p/muxers/mplex/lpchannel.nim b/libp2p/muxers/mplex/lpchannel.nim
index 6ffed67d8..6e1b2a19f 100644
--- a/libp2p/muxers/mplex/lpchannel.nim
+++ b/libp2p/muxers/mplex/lpchannel.nim
@@ -158,11 +158,12 @@ method readUntil*(s: LPChannel,
   await s.tryCleanup()
 
 template writePrefix: untyped =
-  if s.isLazy and not s.isOpen:
-    await s.open()
   if s.closedLocal or s.isReset:
     raise newLPStreamEOFError()
 
+  if s.isLazy and not s.isOpen:
+    await s.open()
+
 method write*(s: LPChannel, pbytes: pointer, nbytes: int) {.async.} =
   writePrefix()
   await procCall write(BufferStream(s), pbytes, nbytes)
diff --git a/libp2p/muxers/mplex/mplex.nim b/libp2p/muxers/mplex/mplex.nim
index 5e758ce8a..54ba181d7 100644
--- a/libp2p/muxers/mplex/mplex.nim
+++ b/libp2p/muxers/mplex/mplex.nim
@@ -11,7 +11,7 @@
 ## Timeouts and message limits are still missing
 ## they need to be added ASAP
 
-import tables, sequtils, options
+import tables, sequtils
 import chronos, chronicles
 import ../muxer,
        ../../connection,
diff --git a/libp2p/switch.nim b/libp2p/switch.nim
index d6715d0fe..f4a7bbdce 100644
--- a/libp2p/switch.nim
+++ b/libp2p/switch.nim
@@ -237,7 +237,9 @@ proc internalConnect(s: Switch,
   else:
     trace "Reusing existing connection"
 
-  await s.subscribeToPeer(peer)
+  if not isNil(conn):
+    await s.subscribeToPeer(peer)
+
   result = conn
 
 proc connect*(s: Switch, peer: PeerInfo) {.async.} =
@@ -323,6 +325,7 @@ proc subscribeToPeer(s: Switch, peerInfo: PeerInfo) {.async, gcsafe.} =
       await s.pubSub.get().subscribeToPeer(conn)
     except CatchableError as exc:
       warn "unable to initiate pubsub", exc = exc.msg
+    finally:
       s.dialedPubSubPeers.excl(peerInfo.id)
 
 proc subscribe*(s: Switch, topic: string,
diff --git a/tests/testinterop.nim b/tests/testinterop.nim
index 1464c4bd7..f519f6397 100644
--- a/tests/testinterop.nim
+++ b/tests/testinterop.nim
@@ -390,6 +390,7 @@ suite "Interop":
         inc(count2)
 
       result = 10 == (await wait(testFuture, 10.secs))
+      await stream.close()
       await nativeNode.stop()
       await allFutures(awaiters)
       await daemonNode.close()