diff --git a/lib/net.js b/lib/net.js
index 998322678e..230d8e3a58 100644
--- a/lib/net.js
+++ b/lib/net.js
@@ -254,8 +254,6 @@ Stream.prototype._appendBucket = function (data, encoding, fd) {
   if (encoding) newBucket.encoding = encoding;
   if (fd) newBucket.fd = fd;
 
-  var queueSize = data.length;
-
   // TODO properly calculate queueSize
 
   if (this._writeWatcher.lastBucket) {
@@ -266,7 +264,13 @@ Stream.prototype._appendBucket = function (data, encoding, fd) {
 
   this._writeWatcher.lastBucket = newBucket;
 
-  return queueSize;
+  if (this._writeWatcher.queueSize === undefined) {
+    this._writeWatcher.queueSize = 0;
+  }
+  assert(this._writeWatcher.queueSize >= 0);
+  this._writeWatcher.queueSize += data.length;
+
+  return this._writeWatcher.queueSize;
 };
 
 
diff --git a/src/node_io_watcher.cc b/src/node_io_watcher.cc
index a991dd9a8f..38f44cc46f 100644
--- a/src/node_io_watcher.cc
+++ b/src/node_io_watcher.cc
@@ -37,6 +37,7 @@ static Persistent<String> fd_sym;
 static Persistent<String> is_unix_socket_sym;
 static Persistent<String> first_bucket_sym;
 static Persistent<String> last_bucket_sym;
+static Persistent<String> queue_size_sym;
 
 
 void IOWatcher::Initialize(Handle<Object> target) {
@@ -62,6 +63,7 @@ void IOWatcher::Initialize(Handle<Object> target) {
   onerror_sym = NODE_PSYMBOL("onerror");
   first_bucket_sym = NODE_PSYMBOL("firstBucket");
   last_bucket_sym = NODE_PSYMBOL("lastBucket");
+  queue_size_sym = NODE_PSYMBOL("queueSize");
   offset_sym = NODE_PSYMBOL("offset");
   fd_sym = NODE_PSYMBOL("fd");
   is_unix_socket_sym = NODE_PSYMBOL("isUnixSocket");
@@ -423,6 +425,9 @@ void IOWatcher::Dump(EV_P_ ev_prepare *w, int revents) {
 
     // what about written == 0 ?
 
+    size_t queue_size = watcher->Get(queue_size_sym)->Uint32Value();
+    assert(queue_size >= offset);
+
     // Now drop the buckets that have been written.
     bucket_index = 0;
 
@@ -451,15 +456,15 @@ void IOWatcher::Dump(EV_P_ ev_prepare *w, int revents) {
       // serialized onto a buffer.
       size_t bucket_len = Buffer::Length(data_v->ToObject());
 
-
       if (unix_socket && bucket->Has(fd_sym)) {
         bucket->Set(fd_sym, Null());
       }
 
-
       assert(bucket_len > offset);
       DEBUG_PRINT("[%ld] bucket_len: %ld, offset: %ld", bucket_index, bucket_len, offset);
 
+      queue_size -= written;
+
       // Only on the first bucket does is the offset > 0.
       if (offset + written < bucket_len) {
         // we have not written the entire bucket
@@ -488,6 +493,9 @@ void IOWatcher::Dump(EV_P_ ev_prepare *w, int revents) {
       watcher->Set(first_bucket_sym, bucket->Get(next_sym));
     }
 
+    // Set the queue size.
+    watcher->Set(queue_size_sym, Integer::NewFromUnsigned(queue_size));
+
     // Finished dumping the buckets.
     //
     // If our list of buckets is empty, we can emit 'drain' and forget about