diff --git a/src/network/socket/qabstractsocket.cpp b/src/network/socket/qabstractsocket.cpp
index d93150799c..5b1c5fa601 100644
--- a/src/network/socket/qabstractsocket.cpp
+++ b/src/network/socket/qabstractsocket.cpp
@@ -2456,13 +2456,15 @@ qint64 QAbstractSocket::readLineData(char *data, qint64 maxlen)
 qint64 QAbstractSocket::writeData(const char *data, qint64 size)
 {
     Q_D(QAbstractSocket);
-    if (d->state == QAbstractSocket::UnconnectedState) {
+    if (d->state == QAbstractSocket::UnconnectedState
+        || (!d->socketEngine && d->socketType != TcpSocket && !d->isBuffered)) {
         d->socketError = QAbstractSocket::UnknownSocketError;
         setErrorString(tr("Socket is not connected"));
         return -1;
     }
 
-    if (!d->isBuffered && d->socketType == TcpSocket && d->writeBuffer.isEmpty()) {
+    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);
         if (written < 0) {
@@ -2473,8 +2475,7 @@ qint64 QAbstractSocket::writeData(const char *data, qint64 size)
             // Buffer what was not written yet
             char *ptr = d->writeBuffer.reserve(size - written);
             memcpy(ptr, data + written, size - written);
-            if (d->socketEngine)
-                d->socketEngine->setWriteNotificationEnabled(true);
+            d->socketEngine->setWriteNotificationEnabled(true);
         }
         return size; // size=actually written + what has been buffered
     } else if (!d->isBuffered && d->socketType != TcpSocket) {
diff --git a/tests/auto/network/socket/qudpsocket/tst_qudpsocket.cpp b/tests/auto/network/socket/qudpsocket/tst_qudpsocket.cpp
index a4695955af..6f96e6d6f5 100644
--- a/tests/auto/network/socket/qudpsocket/tst_qudpsocket.cpp
+++ b/tests/auto/network/socket/qudpsocket/tst_qudpsocket.cpp
@@ -117,6 +117,7 @@ private slots:
     void readyRead();
     void readyReadForEmptyDatagram();
     void asyncReadDatagram();
+    void writeInHostLookupState();
 
 protected slots:
     void empty_readyReadSlot();
@@ -1725,5 +1726,17 @@ void tst_QUdpSocket::asyncReadDatagram()
     delete m_asyncReceiver;
 }
 
+void tst_QUdpSocket::writeInHostLookupState()
+{
+    QFETCH_GLOBAL(bool, setProxy);
+    if (setProxy)
+        return;
+
+    QUdpSocket socket;
+    socket.connectToHost("nosuchserver.qt-project.org", 80);
+    QCOMPARE(socket.state(), QUdpSocket::HostLookupState);
+    QVERIFY(!socket.putChar('0'));
+}
+
 QTEST_MAIN(tst_QUdpSocket)
 #include "tst_qudpsocket.moc"