diff --git a/lib/net/pool.js b/lib/net/pool.js
index f6479859..c601e5ca 100644
--- a/lib/net/pool.js
+++ b/lib/net/pool.js
@@ -114,6 +114,7 @@ function Pool(options) {
   this.uid = 0;
   this.createServer = null;
   this.locker = new Locker();
+  this.dnsLock = new Locker();
   this.proxyServer = null;
   this.auth = null;
   this.identityKey = null;
@@ -1539,16 +1540,40 @@ Pool.prototype.addOutbound = function addOutbound() {
  * @private
  */
 
-Pool.prototype.fillPeers = function fillPeers() {
+Pool.prototype.fillPeers = co(function* fillPeers() {
+  var unlock = yield this.dnsLock.lock();
+  try {
+    return yield this._fillPeers();
+  } finally {
+    unlock();
+  }
+});
+
+/**
+ * Attempt to refill the pool with peers (no lock).
+ * @private
+ */
+
+Pool.prototype._fillPeers = co(function* fillPeers() {
+  var need = this.maxOutbound - this.peers.outbound;
   var i;
 
+  if (need <= 0)
+    return;
+
   this.logger.debug('Refilling peers (%d/%d).',
     this.peers.outbound,
     this.maxOutbound);
 
-  for (i = 0; i < this.maxOutbound - 1; i++)
+  if (this.hosts.size() < need) {
+    this.logger.warning('Very few hosts available.');
+    this.logger.warning('Hitting DNS seeds again.');
+    yield this.hosts.discover(this.maxOutbound * 4);
+  }
+
+  for (i = 0; i < need; i++)
     this.addOutbound();
-};
+});
 
 /**
  * Remove a peer from any list. Drop all load requests.
@@ -2316,15 +2341,18 @@ HostList.prototype.addSeed = function addSeed(hostname) {
  * @returns {Promise}
  */
 
-HostList.prototype.discover = co(function* discover() {
+HostList.prototype.discover = co(function* discover(total) {
   var i, seed;
 
+  if (!total)
+    total = 16;
+
   for (i = 0; i < this.seeds.length; i++) {
     seed = this.seeds[i];
 
     yield this.populate(seed);
 
-    if (this.list.size >= this.maxOutbound * 2)
+    if (this.list.size >= total)
       break;
   }
 });