diff --git a/libp2p/connmanager.nim b/libp2p/connmanager.nim
index 36fbe6d..ad37f00 100644
--- a/libp2p/connmanager.nim
+++ b/libp2p/connmanager.nim
@@ -208,8 +208,8 @@ proc delConn(c: ConnManager, conn: Connection) =
 
     if c.conns[peerId].len == 0:
       c.conns.del(peerId)
-      libp2p_peers.set(c.conns.len.int64)
 
+    libp2p_peers.set(c.conns.len.int64)
     trace "Removed connection", conn
 
 proc cleanupConn(c: ConnManager, conn: Connection) {.async.} =
@@ -327,6 +327,10 @@ proc storeConn*(c: ConnManager, conn: Connection) =
   if isNil(conn):
     raise newException(CatchableError, "connection cannot be nil")
 
+  if conn.closed() or conn.atEof():
+    trace "Can't store dead connection", conn
+    raise newException(CatchableError, "can't store dead connection")
+
   if isNil(conn.peerInfo):
     raise newException(CatchableError, "empty peer info")
 
@@ -370,6 +374,9 @@ proc storeMuxer*(c: ConnManager,
   if isNil(muxer.connection):
     raise newException(CatchableError, "muxer's connection cannot be nil")
 
+  if muxer.connection notin c:
+    raise newException(CatchableError, "cant add muxer for untracked connection")
+
   c.muxed[muxer.connection] = MuxerHolder(
     muxer: muxer,
     handle: handle)
diff --git a/libp2p/stream/bufferstream.nim b/libp2p/stream/bufferstream.nim
index 69e4e57..60a551d 100644
--- a/libp2p/stream/bufferstream.nim
+++ b/libp2p/stream/bufferstream.nim
@@ -64,7 +64,9 @@ method pushData*(s: BufferStream, data: seq[byte]) {.base, async.} =
   ## `pushTo` will block if the queue is full, thus maintaining backpressure.
   ##
 
-  doAssert(not s.pushing, "Only one concurrent push allowed")
+  doAssert(not s.pushing,
+    &"Only one concurrent push allowed for stream {s.shortLog()}")
+
   if s.isClosed or s.pushedEof:
     raise newLPStreamEOFError()
 
@@ -84,7 +86,8 @@ method pushEof*(s: BufferStream) {.base, async.} =
   if s.pushedEof:
     return
 
-  doAssert(not s.pushing, "Only one concurrent push allowed")
+  doAssert(not s.pushing,
+    &"Only one concurrent push allowed for stream {s.shortLog()}")
 
   s.pushedEof = true
 
@@ -105,7 +108,8 @@ method readOnce*(s: BufferStream,
                  nbytes: int):
                  Future[int] {.async.} =
   doAssert(nbytes > 0, "nbytes must be positive integer")
-  doAssert(not s.reading, "Only one concurrent read allowed")
+  doAssert(not s.reading,
+    &"Only one concurrent read allowed for stream {s.shortLog()}")
 
   if s.returnedEof:
     raise newLPStreamEOFError()
diff --git a/libp2p/switch.nim b/libp2p/switch.nim
index 3a67ef1..d254ae6 100644
--- a/libp2p/switch.nim
+++ b/libp2p/switch.nim
@@ -172,6 +172,14 @@ proc mux(s: Switch, conn: Connection): Future[Muxer] {.async, gcsafe.} =
   # store it in muxed connections if we have a peer for it
   s.connManager.storeMuxer(muxer, muxer.handle()) # store muxer and start read loop
 
+  try:
+    await s.identify(muxer)
+  except CatchableError as exc:
+    # Identify is non-essential, though if it fails, it might indicate that
+    # the connection was closed already - this will be picked up by the read
+    # loop
+    debug "Could not identify connection", conn, msg = exc.msg
+
   return muxer
 
 proc disconnect*(s: Switch, peerId: PeerID): Future[void] {.gcsafe.} =
@@ -195,18 +203,10 @@ proc upgradeOutgoing(s: Switch, conn: Connection): Future[Connection] {.async, g
     raise newException(UpgradeFailedError,
       "a muxer is required for outgoing connections")
 
-  try:
-    await s.identify(muxer)
-  except CatchableError as exc:
-    # Identify is non-essential, though if it fails, it might indicate that
-    # the connection was closed already - this will be picked up by the read
-    # loop
-    debug "Could not identify connection", conn, msg = exc.msg
-
-  if isNil(sconn.peerInfo):
+  if sconn.closed() or isNil(sconn.peerInfo):
     await sconn.close()
     raise newException(UpgradeFailedError,
-      "No peerInfo for connection, stopping upgrade")
+      "Connection closed or missing peer info, stopping upgrade")
 
   trace "Upgraded outgoing connection", conn, sconn
 
@@ -302,14 +302,13 @@ proc internalConnect(s: Switch,
   if s.peerInfo.peerId == peerId:
     raise newException(CatchableError, "can't dial self!")
 
-  var conn: Connection
   # Ensure there's only one in-flight attempt per peer
   let lock = s.dialLock.mgetOrPut(peerId, newAsyncLock())
   try:
     await lock.acquire()
 
     # Check if we have a connection already and try to reuse it
-    conn = s.connManager.selectConn(peerId)
+    var conn = s.connManager.selectConn(peerId)
     if conn != nil:
       if conn.atEof or conn.closed:
         # This connection should already have been removed from the connection
@@ -323,22 +322,25 @@ proc internalConnect(s: Switch,
       return conn
 
     conn = await s.dialAndUpgrade(peerId, addrs)
+    if isNil(conn): # None of the addresses connected
+      raise newException(DialFailedError, "Unable to establish outgoing link")
+
+    # We already check for this in Connection manager
+    # but a disconnect could have happened right after
+    # we've added the connection so we check again
+    # to prevent races due to that.
+    if conn.closed() or conn.atEof():
+      # This can happen when the other ends drops us
+      # before we get a chance to return the connection
+      # back to the dialer.
+      trace "Connection dead on arrival", conn
+      raise newLPStreamClosedError()
+
+    return conn
   finally:
     if lock.locked():
       lock.release()
 
-  if isNil(conn): # None of the addresses connected
-    raise newException(DialFailedError, "Unable to establish outgoing link")
-
-  if conn.closed() or conn.atEof():
-    # This can happen when the other ends drops us
-    # before we get a chance to return the connection
-    # back to the dialer.
-    trace "Connection dead on arrival", conn
-    raise newLPStreamClosedError()
-
-  return conn
-
 proc connect*(s: Switch, peerId: PeerID, addrs: seq[MultiAddress]) {.async.} =
   discard await s.internalConnect(peerId, addrs)
 
diff --git a/tests/testconnmngr.nim b/tests/testconnmngr.nim
index 8afad8a..f700200 100644
--- a/tests/testconnmngr.nim
+++ b/tests/testconnmngr.nim
@@ -38,6 +38,29 @@ suite "Connection Manager":
 
     await connMngr.close()
 
+  asyncTest "shouldn't allow a closed connection":
+    let connMngr = ConnManager.init()
+    let peer = PeerInfo.init(PrivateKey.random(ECDSA, (newRng())[]).tryGet())
+    let conn = Connection.init(peer, Direction.In)
+    await conn.close()
+
+    expect CatchableError:
+      connMngr.storeConn(conn)
+
+    await connMngr.close()
+
+  asyncTest "shouldn't allow an EOFed connection":
+    let connMngr = ConnManager.init()
+    let peer = PeerInfo.init(PrivateKey.random(ECDSA, (newRng())[]).tryGet())
+    let conn = Connection.init(peer, Direction.In)
+    conn.isEof = true
+
+    expect CatchableError:
+      connMngr.storeConn(conn)
+
+    await conn.close()
+    await connMngr.close()
+
   asyncTest "add and retrieve a muxer":
     let connMngr = ConnManager.init()
     let peer = PeerInfo.init(PrivateKey.random(ECDSA, (newRng())[]).tryGet())
@@ -54,6 +77,20 @@ suite "Connection Manager":
 
     await connMngr.close()
 
+  asyncTest "shouldn't allow a muxer for an untracked connection":
+    let connMngr = ConnManager.init()
+    let peer = PeerInfo.init(PrivateKey.random(ECDSA, (newRng())[]).tryGet())
+    let conn = Connection.init(peer, Direction.In)
+    let muxer = new Muxer
+    muxer.connection = conn
+
+    expect CatchableError:
+      connMngr.storeMuxer(muxer)
+
+    await conn.close()
+    await muxer.close()
+    await connMngr.close()
+
   asyncTest "get conn with direction":
     let connMngr = ConnManager.init()
     let peer = PeerInfo.init(PrivateKey.random(ECDSA, (newRng())[]).tryGet())
diff --git a/tests/testmplex.nim b/tests/testmplex.nim
index 19d3082..028a5bb 100644
--- a/tests/testmplex.nim
+++ b/tests/testmplex.nim
@@ -907,7 +907,7 @@ suite "Mplex":
 
       checkTracker(LPChannelTrackerName)
 
-      await conn.close()
+      await conn.closeWithEOF()
       await mplexDialFut
       await allFuturesThrowing(
         transport1.stop(),
@@ -943,7 +943,8 @@ suite "Mplex":
       for i in 0..9:
         dialStreams.add((await mplexDial.newStream()))
 
-      await listenConn.close()
+      await sleepAsync(100.millis)
+      await listenConn.closeWithEOF()
       await allFuturesThrowing(
           (dialStreams & listenStreams)
           .mapIt( it.join() ))
diff --git a/tests/testswitch.nim b/tests/testswitch.nim
index 4786f85..b77cff9 100644
--- a/tests/testswitch.nim
+++ b/tests/testswitch.nim
@@ -672,7 +672,7 @@ suite "Switch":
 
     proc acceptHandler() {.async, gcsafe.} =
       let conn = await transport.accept()
-      await conn.close()
+      await conn.closeWithEOF()
 
     let handlerWait = acceptHandler()
     let switch = newStandardSwitch(secureManagers = [SecureProtocol.Noise])