diff --git a/lib/net.js b/lib/net.js
index 6aa1453d65..90e8cf7e3c 100644
--- a/lib/net.js
+++ b/lib/net.js
@@ -118,7 +118,7 @@ function setImplmentationMethods(self) {
       // emitting the same value that we see now. Otherwise, we can end up
       // calling emit() after recvMsg() has been called again and end up
       // emitting null (or another FD).
-      if (recvMsg.fd !== null) {
+      if (typeof recvMsg.fd === 'number') {
         var fd = recvMsg.fd;
         process.nextTick(function() {
           self.emit('fd', fd);
@@ -251,16 +251,16 @@ Object.defineProperty(Socket.prototype, 'readyState', {
     if (this._connecting) {
       return 'opening';
     } else if (this.readable && this.writable) {
-      assert(typeof this.fd == 'number');
+      assert(typeof this.fd === 'number');
       return 'open';
     } else if (this.readable && !this.writable) {
-      assert(typeof this.fd == 'number');
+      assert(typeof this.fd === 'number');
       return 'readOnly';
     } else if (!this.readable && this.writable) {
-      assert(typeof this.fd == 'number');
+      assert(typeof this.fd === 'number');
       return 'writeOnly';
     } else {
-      assert(typeof this.fd != 'number');
+      assert(typeof this.fd !== 'number');
       return 'closed';
     }
   }
@@ -665,7 +665,7 @@ Socket.prototype._onReadable = function() {
 Socket.prototype.connect = function() {
   var self = this;
   initSocket(self);
-  if (self.fd) throw new Error('Socket already opened');
+  if (typeof self.fd === 'number') throw new Error('Socket already opened');
   if (!self._readWatcher) throw new Error('No readWatcher');
 
   timers.active(this);
@@ -723,7 +723,7 @@ Socket.prototype.setKeepAlive = function(enable, time) {
 Socket.prototype.setTimeout = function(msecs, callback) {
   if (msecs > 0) {
     timers.enroll(this, msecs);
-    if (this.fd) { timers.active(this); }
+    if (typeof this.fd === 'number') { timers.active(this); }
     if (callback) {
       this.once('timeout', callback);
     }
@@ -739,7 +739,9 @@ Socket.prototype.pause = function() {
 
 
 Socket.prototype.resume = function() {
-  if (this.fd === null) throw new Error('Cannot resume() closed Socket.');
+  if (typeof this.fd !== 'number') {
+    throw new Error('Cannot resume() closed Socket.');
+  }
   if (this._readWatcher) {
     this._readWatcher.stop();
     this._readWatcher.set(this.fd, true, false);
@@ -793,7 +795,7 @@ Socket.prototype.destroy = function(exception) {
   }
 
   // FIXME Bug when this.fd == 0
-  if (typeof this.fd == 'number') {
+  if (typeof this.fd === 'number') {
     debug('close ' + this.fd);
     close(this.fd);
     this.fd = null;
@@ -986,7 +988,7 @@ Server.prototype._rejectPending = function() {
 // server.listen(8000, '192.168.1.2');
 Server.prototype.listen = function() {
   var self = this;
-  if (self.fd) throw new Error('Server already opened');
+  if (typeof self.fd === 'number') throw new Error('Server already opened');
 
   var lastArg = arguments[arguments.length - 1];
   if (typeof lastArg == 'function') {
@@ -1041,7 +1043,7 @@ Server.prototype.listen = function() {
 };
 
 Server.prototype.listenFD = function(fd, type) {
-  if (this.fd) {
+  if (typeof this.fd === 'number') {
     throw new Error('Server already opened');
   }
 
@@ -1076,7 +1078,7 @@ Server.prototype._doListen = function() {
     // It could be that server.close() was called between the time the
     // original listen command was issued and this. Bail if that's the case.
     // See test/simple/test-net-eaddrinuse.js
-    if (typeof self.fd != 'number') return;
+    if (typeof self.fd !== 'number') return;
 
     try {
       listen(self.fd, self._backlog || 128);