diff --git a/src/network/socket/qabstractsocket.cpp b/src/network/socket/qabstractsocket.cpp
index 3d665270fd..f28dc6698a 100644
--- a/src/network/socket/qabstractsocket.cpp
+++ b/src/network/socket/qabstractsocket.cpp
@@ -881,7 +881,7 @@ bool QAbstractSocketPrivate::flush()
     const char *ptr = writeBuffer.readPointer();
 
     // Attempt to write it all in one chunk.
-    qint64 written = socketEngine->write(ptr, nextSize);
+    qint64 written = nextSize ? socketEngine->write(ptr, nextSize) : Q_INT64_C(0);
     if (written < 0) {
 #if defined (QABSTRACTSOCKET_DEBUG)
         qDebug() << "QAbstractSocketPrivate::flush() write error, aborting." << socketEngine->errorString();
@@ -2477,7 +2477,7 @@ qint64 QAbstractSocket::writeData(const char *data, qint64 size)
     if (!d->isBuffered && d->socketType == TcpSocket
         && d->socketEngine && d->writeBuffer.isEmpty()) {
         // This code is for the new Unbuffered QTcpSocket use case
-        qint64 written = d->socketEngine->write(data, size);
+        qint64 written = size ? d->socketEngine->write(data, size) : Q_INT64_C(0);
         if (written < 0) {
             d->setError(d->socketEngine->error(), d->socketEngine->errorString());
             return written;
diff --git a/src/network/socket/qnativesocketengine.cpp b/src/network/socket/qnativesocketengine.cpp
index 805acde860..86d13d82a2 100644
--- a/src/network/socket/qnativesocketengine.cpp
+++ b/src/network/socket/qnativesocketengine.cpp
@@ -846,6 +846,10 @@ qint64 QNativeSocketEngine::writeDatagram(const char *data, qint64 size, const Q
 /*!
     Writes a block of \a size bytes from \a data to the socket.
     Returns the number of bytes written, or -1 if an error occurred.
+
+    Passing zero as the \a size parameter on a connected UDP socket
+    will send an empty datagram. For other socket types results are
+    unspecified.
 */
 qint64 QNativeSocketEngine::write(const char *data, qint64 size)
 {