diff --git a/lib/server/swarm.js b/lib/server/swarm.js
index 84c2705b..43df8106 100644
--- a/lib/server/swarm.js
+++ b/lib/server/swarm.js
@@ -7,6 +7,7 @@ var randomIterate = require('random-iterate')
 // need to support when overriding Server.getSwarm()
 function Swarm (infoHash, server) {
   this.peers = {}
+  this.interval = server.intervalMs
   this.complete = 0
   this.incomplete = 0
 }
@@ -54,7 +55,8 @@ Swarm.prototype._onAnnounceStarted = function (params, peer) {
     peerId: params.peer_id, // as hex
     ip: params.ip, // only http, udp
     port: params.port, // only http, udp
-    socket: params.socket // only websocket
+    socket: params.socket, // only websocket
+    lastSeen: Date.now()
   }
 }
 
@@ -89,6 +91,8 @@ Swarm.prototype._onAnnounceUpdate = function (params, peer) {
     debug('unexpected `update` event from peer that is not in swarm')
     return this._onAnnounceStarted(params, peer) // treat as a start
   }
+  
+  peer.lastSeen = Date.now()
 
   if (!peer.complete && params.left === 0) {
     this.complete += 1
@@ -101,9 +105,19 @@ Swarm.prototype._getPeers = function (numwant, isWebRTC) {
   var peers = []
   var ite = randomIterate(Object.keys(this.peers))
   var peerId
+  
+  // allow peers to skip one announce interval before blacklisting
+  var blacklistMaximum = Date.now() - 2 * this.interval
+  
   while ((peerId = ite()) && peers.length < numwant) {
     var peer = this.peers[peerId]
     if (!peer) continue
+    
+    // blacklist peers which aren't announing
+    // changing their ports to another
+    if (peer.lastSeen < blacklistMaximum) {
+      peer.port = 1
+    }
     if ((isWebRTC && peer.socket) || (!isWebRTC && peer.ip)) peers.push(peer)
   }
   return peers