Replace manual xmlns writing by writeDefaultNamespace()

This is the result of:

sed -i 's/writeAttribute("xmlns", /writeDefaultNamespace(/g' \
	$(find . -iname "*.cpp" -or -iname "*.h")

36 files changed, 90 insertions, 90 deletions

diff --git a/src/base/QXmppArchiveIq.cpp b/src/base/QXmppArchiveIq.cpp
index 34b73b50..de3fbed8 100644
--- a/src/base/QXmppArchiveIq.cpp
+++ b/src/base/QXmppArchiveIq.cpp
@@ -114,7 +114,7 @@ void QXmppArchiveChat::parse(const QDomElement &element)
 void QXmppArchiveChat::toXml(QXmlStreamWriter *writer, const QXmppResultSetReply &rsm) const
 {
     writer->writeStartElement("chat");
-    writer->writeAttribute("xmlns", ns_archive);
+    writer->writeDefaultNamespace(ns_archive);
     helperToXmlAddAttribute(writer, "with", m_with);
     if (m_start.isValid())
         helperToXmlAddAttribute(writer, "start", QXmppUtils::datetimeToString(m_start));
@@ -416,7 +416,7 @@ void QXmppArchiveListIq::parseElementFromChild(const QDomElement &element)
 void QXmppArchiveListIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("list");
-    writer->writeAttribute("xmlns", ns_archive);
+    writer->writeDefaultNamespace(ns_archive);
     if (!m_with.isEmpty())
         helperToXmlAddAttribute(writer, "with", m_with);
     if (m_start.isValid())
@@ -447,7 +447,7 @@ void QXmppArchivePrefIq::parseElementFromChild(const QDomElement &element)
 void QXmppArchivePrefIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("pref");
-    writer->writeAttribute("xmlns", ns_archive);
+    writer->writeDefaultNamespace(ns_archive);
     writer->writeEndElement();
 }
 /// \endcond
@@ -521,7 +521,7 @@ void QXmppArchiveRemoveIq::parseElementFromChild(const QDomElement &element)
 void QXmppArchiveRemoveIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("remove");
-    writer->writeAttribute("xmlns", ns_archive);
+    writer->writeDefaultNamespace(ns_archive);
     if (!m_with.isEmpty())
         helperToXmlAddAttribute(writer, "with", m_with);
     if (m_start.isValid())
@@ -608,7 +608,7 @@ void QXmppArchiveRetrieveIq::parseElementFromChild(const QDomElement &element)
 void QXmppArchiveRetrieveIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("retrieve");
-    writer->writeAttribute("xmlns", ns_archive);
+    writer->writeDefaultNamespace(ns_archive);
     helperToXmlAddAttribute(writer, "with", m_with);
     helperToXmlAddAttribute(writer, "start", QXmppUtils::datetimeToString(m_start));
     if (!m_rsmQuery.isNull())
diff --git a/src/base/QXmppBindIq.cpp b/src/base/QXmppBindIq.cpp
index 1e1bfa51..b0351980 100644
--- a/src/base/QXmppBindIq.cpp
+++ b/src/base/QXmppBindIq.cpp
@@ -81,7 +81,7 @@ void QXmppBindIq::parseElementFromChild(const QDomElement &element)
 void QXmppBindIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("bind");
-    writer->writeAttribute("xmlns", ns_bind);
+    writer->writeDefaultNamespace(ns_bind);
     if (!m_jid.isEmpty())
         helperToXmlAddTextElement(writer, "jid", m_jid);
     if (!m_resource.isEmpty())
diff --git a/src/base/QXmppBitsOfBinaryData.cpp b/src/base/QXmppBitsOfBinaryData.cpp
index 503eabc0..f3eba9cb 100644
--- a/src/base/QXmppBitsOfBinaryData.cpp
+++ b/src/base/QXmppBitsOfBinaryData.cpp
@@ -148,7 +148,7 @@ void QXmppBitsOfBinaryData::parseElementFromChild(const QDomElement &dataElement
 void QXmppBitsOfBinaryData::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("data");
-    writer->writeAttribute("xmlns", ns_bob);
+    writer->writeDefaultNamespace(ns_bob);
     helperToXmlAddAttribute(writer, "cid", d->cid.toContentId());
     if (d->maxAge > -1)
         helperToXmlAddAttribute(writer, "max-age", QString::number(d->maxAge));
diff --git a/src/base/QXmppBookmarkSet.cpp b/src/base/QXmppBookmarkSet.cpp
index a47234b2..e70adcc6 100644
--- a/src/base/QXmppBookmarkSet.cpp
+++ b/src/base/QXmppBookmarkSet.cpp
@@ -209,7 +209,7 @@ void QXmppBookmarkSet::parse(const QDomElement &element)
 void QXmppBookmarkSet::toXml(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("storage");
-    writer->writeAttribute("xmlns", ns_bookmarks);
+    writer->writeDefaultNamespace(ns_bookmarks);
     for (const auto &conference : m_conferences) {
         writer->writeStartElement("conference");
         if (conference.autoJoin())
diff --git a/src/base/QXmppByteStreamIq.cpp b/src/base/QXmppByteStreamIq.cpp
index 29f008a2..92709b4d 100644
--- a/src/base/QXmppByteStreamIq.cpp
+++ b/src/base/QXmppByteStreamIq.cpp
@@ -154,7 +154,7 @@ void QXmppByteStreamIq::parseElementFromChild(const QDomElement &element)
 void QXmppByteStreamIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("query");
-    writer->writeAttribute("xmlns", ns_bytestreams);
+    writer->writeDefaultNamespace(ns_bytestreams);
     helperToXmlAddAttribute(writer, "sid", m_sid);
     QString modeStr;
     if (m_mode == Tcp)
diff --git a/src/base/QXmppDataForm.cpp b/src/base/QXmppDataForm.cpp
index 7e39236f..7face338 100644
--- a/src/base/QXmppDataForm.cpp
+++ b/src/base/QXmppDataForm.cpp
@@ -750,7 +750,7 @@ void QXmppDataForm::toXml(QXmlStreamWriter *writer) const
         return;
 
     writer->writeStartElement("x");
-    writer->writeAttribute("xmlns", ns_data);
+    writer->writeDefaultNamespace(ns_data);
 
     /* form type */
     QString typeStr;
diff --git a/src/base/QXmppDiscoveryIq.cpp b/src/base/QXmppDiscoveryIq.cpp
index ef8baa6f..6524e81f 100644
--- a/src/base/QXmppDiscoveryIq.cpp
+++ b/src/base/QXmppDiscoveryIq.cpp
@@ -306,7 +306,7 @@ void QXmppDiscoveryIq::parseElementFromChild(const QDomElement &element)
 void QXmppDiscoveryIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("query");
-    writer->writeAttribute("xmlns",
+    writer->writeDefaultNamespace(
         m_queryType == InfoQuery ? ns_disco_info : ns_disco_items);
     helperToXmlAddAttribute(writer, "node", m_queryNode);
 
diff --git a/src/base/QXmppElement.cpp b/src/base/QXmppElement.cpp
index 7570dbcf..fbf8762c 100644
--- a/src/base/QXmppElement.cpp
+++ b/src/base/QXmppElement.cpp
@@ -237,7 +237,7 @@ void QXmppElement::toXml(QXmlStreamWriter *writer) const
 
     writer->writeStartElement(d->name);
     if (d->attributes.contains("xmlns"))
-        writer->writeAttribute("xmlns", d->attributes.value("xmlns"));
+        writer->writeDefaultNamespace(d->attributes.value("xmlns"));
     for (const auto &attr : d->attributes.keys())
         if (attr != "xmlns")
             helperToXmlAddAttribute(writer, attr, d->attributes.value(attr));
diff --git a/src/base/QXmppEntityTimeIq.cpp b/src/base/QXmppEntityTimeIq.cpp
index 17da460a..9dad7ce0 100644
--- a/src/base/QXmppEntityTimeIq.cpp
+++ b/src/base/QXmppEntityTimeIq.cpp
@@ -80,7 +80,7 @@ void QXmppEntityTimeIq::parseElementFromChild(const QDomElement &element)
 void QXmppEntityTimeIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("time");
-    writer->writeAttribute("xmlns", ns_entity_time);
+    writer->writeDefaultNamespace(ns_entity_time);
 
     if(m_utc.isValid())
     {
diff --git a/src/base/QXmppHttpUploadIq.cpp b/src/base/QXmppHttpUploadIq.cpp
index 82432d7b..932f5504 100644
--- a/src/base/QXmppHttpUploadIq.cpp
+++ b/src/base/QXmppHttpUploadIq.cpp
@@ -119,7 +119,7 @@ void QXmppHttpUploadRequestIq::parseElementFromChild(const QDomElement &element)
 void QXmppHttpUploadRequestIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("request");
-    writer->writeAttribute("xmlns", ns_http_upload);
+    writer->writeDefaultNamespace(ns_http_upload);
     // filename and size are required
     writer->writeAttribute("filename", d->fileName);
     writer->writeAttribute("size", QString::number(d->size));
@@ -231,7 +231,7 @@ void QXmppHttpUploadSlotIq::parseElementFromChild(const QDomElement &element)
 void QXmppHttpUploadSlotIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("slot");
-    writer->writeAttribute("xmlns", ns_http_upload);
+    writer->writeDefaultNamespace(ns_http_upload);
 
     writer->writeStartElement("put");
     writer->writeAttribute("url", d->putUrl.toEncoded());
diff --git a/src/base/QXmppIbbIq.cpp b/src/base/QXmppIbbIq.cpp
index dbe3ab97..7f79140b 100644
--- a/src/base/QXmppIbbIq.cpp
+++ b/src/base/QXmppIbbIq.cpp
@@ -70,7 +70,7 @@ void QXmppIbbOpenIq::parseElementFromChild(const QDomElement &element)
 void QXmppIbbOpenIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("open");
-    writer->writeAttribute( "xmlns",ns_ibb);
+    writer->writeDefaultNamespace(ns_ibb);
     writer->writeAttribute( "sid",m_sid);
     writer->writeAttribute( "block-size",QString::number(m_block_size) );
     writer->writeEndElement();
@@ -108,7 +108,7 @@ void QXmppIbbCloseIq::parseElementFromChild(const QDomElement &element)
 void QXmppIbbCloseIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("close");
-    writer->writeAttribute( "xmlns",ns_ibb);
+    writer->writeDefaultNamespace(ns_ibb);
     writer->writeAttribute( "sid",m_sid);
     writer->writeEndElement();
 }
@@ -166,7 +166,7 @@ void QXmppIbbDataIq::parseElementFromChild(const QDomElement &element)
 void QXmppIbbDataIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("data");
-    writer->writeAttribute( "xmlns",ns_ibb);
+    writer->writeDefaultNamespace(ns_ibb);
     writer->writeAttribute( "sid",m_sid);
     writer->writeAttribute( "seq",QString::number(m_seq) );
     writer->writeCharacters( m_payload.toBase64() );
diff --git a/src/base/QXmppJingleIq.cpp b/src/base/QXmppJingleIq.cpp
index 3acdca6a..4c0be456 100644
--- a/src/base/QXmppJingleIq.cpp
+++ b/src/base/QXmppJingleIq.cpp
@@ -422,7 +422,7 @@ void QXmppJingleIq::Content::toXml(QXmlStreamWriter *writer) const
     if (!d->descriptionType.isEmpty() || !d->payloadTypes.isEmpty())
     {
         writer->writeStartElement("description");
-        writer->writeAttribute("xmlns", d->descriptionType);
+        writer->writeDefaultNamespace(d->descriptionType);
         helperToXmlAddAttribute(writer, "media", d->descriptionMedia);
         if (d->descriptionSsrc)
             writer->writeAttribute("ssrc", QString::number(d->descriptionSsrc));
@@ -435,7 +435,7 @@ void QXmppJingleIq::Content::toXml(QXmlStreamWriter *writer) const
     if (!d->transportType.isEmpty() || !d->transportCandidates.isEmpty())
     {
         writer->writeStartElement("transport");
-        writer->writeAttribute("xmlns", d->transportType);
+        writer->writeDefaultNamespace(d->transportType);
         helperToXmlAddAttribute(writer, "ufrag", d->transportUser);
         helperToXmlAddAttribute(writer, "pwd", d->transportPassword);
         for (const auto &candidate : d->transportCandidates)
@@ -444,7 +444,7 @@ void QXmppJingleIq::Content::toXml(QXmlStreamWriter *writer) const
         // XEP-0320
         if (!d->transportFingerprint.isEmpty() && !d->transportFingerprintHash.isEmpty()) {
             writer->writeStartElement("fingerprint");
-            writer->writeAttribute("xmlns", ns_jingle_dtls);
+            writer->writeDefaultNamespace(ns_jingle_dtls);
             writer->writeAttribute("hash", d->transportFingerprintHash);
             writer->writeAttribute("setup", d->transportFingerprintSetup);
             writer->writeCharacters(formatFingerprint(d->transportFingerprint));
@@ -902,7 +902,7 @@ void QXmppJingleIq::parseElementFromChild(const QDomElement &element)
 void QXmppJingleIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("jingle");
-    writer->writeAttribute("xmlns", ns_jingle);
+    writer->writeDefaultNamespace(ns_jingle);
     helperToXmlAddAttribute(writer, "action", jingle_actions[d->action]);
     helperToXmlAddAttribute(writer, "initiator", d->initiator);
     helperToXmlAddAttribute(writer, "responder", d->responder);
@@ -914,7 +914,7 @@ void QXmppJingleIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
     // ringing
     if (d->ringing) {
         writer->writeStartElement("ringing");
-        writer->writeAttribute("xmlns", ns_jingle_rtp_info);
+        writer->writeDefaultNamespace(ns_jingle_rtp_info);
         writer->writeEndElement();
     }
 
diff --git a/src/base/QXmppMamIq.cpp b/src/base/QXmppMamIq.cpp
index cb50cdd4..c2a719e4 100644
--- a/src/base/QXmppMamIq.cpp
+++ b/src/base/QXmppMamIq.cpp
@@ -116,7 +116,7 @@ void QXmppMamQueryIq::parseElementFromChild(const QDomElement &element)
 void QXmppMamQueryIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("query");
-    writer->writeAttribute("xmlns", ns_mam);
+    writer->writeDefaultNamespace(ns_mam);
     if (!m_node.isEmpty()) {
         writer->writeAttribute("node", m_node);
     }
@@ -185,7 +185,7 @@ void QXmppMamResultIq::parseElementFromChild(const QDomElement &element)
 void QXmppMamResultIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("fin");
-    writer->writeAttribute("xmlns", ns_mam);
+    writer->writeDefaultNamespace(ns_mam);
     if (m_complete) {
         writer->writeAttribute("complete", "true");
     }
diff --git a/src/base/QXmppMessage.cpp b/src/base/QXmppMessage.cpp
index f11a9cb5..4f50b836 100644
--- a/src/base/QXmppMessage.cpp
+++ b/src/base/QXmppMessage.cpp
@@ -849,16 +849,16 @@ void QXmppMessage::toXml(QXmlStreamWriter *xmlWriter) const
     // chat states
     if (d->state > None && d->state <= Paused) {
         xmlWriter->writeStartElement(CHAT_STATES.at(d->state));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_chat_states);
+        xmlWriter->writeDefaultNamespace(ns_chat_states);
         xmlWriter->writeEndElement();
     }
 
     // XEP-0071: XHTML-IM
     if (!d->xhtml.isEmpty()) {
         xmlWriter->writeStartElement(QStringLiteral("html"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_xhtml_im);
+        xmlWriter->writeDefaultNamespace(ns_xhtml_im);
         xmlWriter->writeStartElement(QStringLiteral("body"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_xhtml);
+        xmlWriter->writeDefaultNamespace(ns_xhtml);
         xmlWriter->writeCharacters(QStringLiteral(""));
         xmlWriter->device()->write(d->xhtml.toUtf8());
         xmlWriter->writeEndElement();
@@ -871,13 +871,13 @@ void QXmppMessage::toXml(QXmlStreamWriter *xmlWriter) const
         if (d->stampType == DelayedDelivery) {
             // XEP-0203: Delayed Delivery
             xmlWriter->writeStartElement(QStringLiteral("delay"));
-            xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_delayed_delivery);
+            xmlWriter->writeDefaultNamespace(ns_delayed_delivery);
             helperToXmlAddAttribute(xmlWriter, QStringLiteral("stamp"), QXmppUtils::datetimeToString(utcStamp));
             xmlWriter->writeEndElement();
         } else {
             // XEP-0091: Legacy Delayed Delivery
             xmlWriter->writeStartElement(QStringLiteral("x"));
-            xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_legacy_delayed_delivery);
+            xmlWriter->writeDefaultNamespace(ns_legacy_delayed_delivery);
             helperToXmlAddAttribute(xmlWriter, QStringLiteral("stamp"), utcStamp.toString(QStringLiteral("yyyyMMddThh:mm:ss")));
             xmlWriter->writeEndElement();
         }
@@ -886,27 +886,27 @@ void QXmppMessage::toXml(QXmlStreamWriter *xmlWriter) const
     // XEP-0184: Message Delivery Receipts
     if (!d->receiptId.isEmpty()) {
         xmlWriter->writeStartElement(QStringLiteral("received"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_message_receipts);
+        xmlWriter->writeDefaultNamespace(ns_message_receipts);
         xmlWriter->writeAttribute(QStringLiteral("id"), d->receiptId);
         xmlWriter->writeEndElement();
     }
     if (d->receiptRequested) {
         xmlWriter->writeStartElement(QStringLiteral("request"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_message_receipts);
+        xmlWriter->writeDefaultNamespace(ns_message_receipts);
         xmlWriter->writeEndElement();
     }
 
     // XEP-0224: Attention
     if (d->attentionRequested) {
         xmlWriter->writeStartElement(QStringLiteral("attention"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_attention);
+        xmlWriter->writeDefaultNamespace(ns_attention);
         xmlWriter->writeEndElement();
     }
 
     // XEP-0249: Direct MUC Invitations
     if (!d->mucInvitationJid.isEmpty()) {
         xmlWriter->writeStartElement(QStringLiteral("x"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_conference);
+        xmlWriter->writeDefaultNamespace(ns_conference);
         xmlWriter->writeAttribute(QStringLiteral("jid"), d->mucInvitationJid);
         if (!d->mucInvitationPassword.isEmpty())
             xmlWriter->writeAttribute(QStringLiteral("password"), d->mucInvitationPassword);
@@ -918,12 +918,12 @@ void QXmppMessage::toXml(QXmlStreamWriter *xmlWriter) const
     // XEP-0333: Chat Markers
     if (d->markable) {
         xmlWriter->writeStartElement(QStringLiteral("markable"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_chat_markers);
+        xmlWriter->writeDefaultNamespace(ns_chat_markers);
         xmlWriter->writeEndElement();
     }
     if (d->marker != NoMarker) {
         xmlWriter->writeStartElement(MARKER_TYPES.at(d->marker));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_chat_markers);
+        xmlWriter->writeDefaultNamespace(ns_chat_markers);
         xmlWriter->writeAttribute(QStringLiteral("id"), d->markedId);
         if (!d->markedThread.isNull() && !d->markedThread.isEmpty()) {
             xmlWriter->writeAttribute(QStringLiteral("thread"), d->markedThread);
@@ -938,14 +938,14 @@ void QXmppMessage::toXml(QXmlStreamWriter *xmlWriter) const
     // XEP-0280: Message Carbons
     if (d->privatemsg) {
         xmlWriter->writeStartElement(QStringLiteral("private"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_carbons);
+        xmlWriter->writeDefaultNamespace(ns_carbons);
         xmlWriter->writeEndElement();
     }
 
     // XEP-0066: Out of Band Data
     if (!d->outOfBandUrl.isEmpty()) {
         xmlWriter->writeStartElement(QStringLiteral("x"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_oob);
+        xmlWriter->writeDefaultNamespace(ns_oob);
         xmlWriter->writeTextElement(QStringLiteral("url"), d->outOfBandUrl);
         xmlWriter->writeEndElement();
     }
@@ -953,7 +953,7 @@ void QXmppMessage::toXml(QXmlStreamWriter *xmlWriter) const
     // XEP-0308: Last Message Correction
     if (!d->replaceId.isEmpty()) {
         xmlWriter->writeStartElement(QStringLiteral("replace"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_message_correct);
+        xmlWriter->writeDefaultNamespace(ns_message_correct);
         xmlWriter->writeAttribute(QStringLiteral("id"), d->replaceId);
         xmlWriter->writeEndElement();
     }
@@ -962,7 +962,7 @@ void QXmppMessage::toXml(QXmlStreamWriter *xmlWriter) const
     for (quint8 i = 0; i < HINT_TYPES.size(); i++) {
         if (hasHint(Hint(1 << i))) {
             xmlWriter->writeStartElement(HINT_TYPES.at(i));
-            xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_message_processing_hints);
+            xmlWriter->writeDefaultNamespace(ns_message_processing_hints);
             xmlWriter->writeEndElement();
         }
     }
@@ -970,7 +970,7 @@ void QXmppMessage::toXml(QXmlStreamWriter *xmlWriter) const
     // XEP-0367: Message Attaching
     if (!d->attachId.isEmpty()) {
         xmlWriter->writeStartElement(QStringLiteral("attach-to"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_message_attaching);
+        xmlWriter->writeDefaultNamespace(ns_message_attaching);
         xmlWriter->writeAttribute(QStringLiteral("id"), d->attachId);
         xmlWriter->writeEndElement();
     }
@@ -978,7 +978,7 @@ void QXmppMessage::toXml(QXmlStreamWriter *xmlWriter) const
     // XEP-0369: Mediated Information eXchange (MIX)
     if (!d->mixUserJid.isEmpty() || !d->mixUserNick.isEmpty()) {
         xmlWriter->writeStartElement(QStringLiteral("mix"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_mix);
+        xmlWriter->writeDefaultNamespace(ns_mix);
         helperToXmlAddTextElement(xmlWriter, QStringLiteral("jid"), d->mixUserJid);
         helperToXmlAddTextElement(xmlWriter, QStringLiteral("nick"), d->mixUserNick);
         xmlWriter->writeEndElement();
@@ -987,7 +987,7 @@ void QXmppMessage::toXml(QXmlStreamWriter *xmlWriter) const
     // XEP-0380: Explicit Message Encryption
     if (!d->encryptionMethod.isEmpty()) {
         xmlWriter->writeStartElement(QStringLiteral("encryption"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_eme);
+        xmlWriter->writeDefaultNamespace(ns_eme);
         xmlWriter->writeAttribute(QStringLiteral("namespace"), d->encryptionMethod);
         helperToXmlAddAttribute(xmlWriter, QStringLiteral("name"), d->encryptionName);
         xmlWriter->writeEndElement();
@@ -996,7 +996,7 @@ void QXmppMessage::toXml(QXmlStreamWriter *xmlWriter) const
     // XEP-0382: Spoiler messages
     if (d->isSpoiler) {
         xmlWriter->writeStartElement(QStringLiteral("spoiler"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_spoiler);
+        xmlWriter->writeDefaultNamespace(ns_spoiler);
         xmlWriter->writeCharacters(d->spoilerHint);
         xmlWriter->writeEndElement();
     }
diff --git a/src/base/QXmppMixIq.cpp b/src/base/QXmppMixIq.cpp
index 0f0afc29..854b86b8 100644
--- a/src/base/QXmppMixIq.cpp
+++ b/src/base/QXmppMixIq.cpp
@@ -184,7 +184,7 @@ void QXmppMixIq::toXmlElementFromChild(QXmlStreamWriter* writer) const
 
     writer->writeStartElement(MIX_ACTION_TYPES.at(d->actionType));
     if (d->actionType == ClientJoin || d->actionType == ClientLeave) {
-        writer->writeAttribute("xmlns", ns_mix_pam);
+        writer->writeDefaultNamespace(ns_mix_pam);
         if (type() == Set)
             helperToXmlAddAttribute(writer, "channel", d->jid);
 
@@ -194,7 +194,7 @@ void QXmppMixIq::toXmlElementFromChild(QXmlStreamWriter* writer) const
             writer->writeStartElement("leave");
     }
 
-    writer->writeAttribute("xmlns", ns_mix);
+    writer->writeDefaultNamespace(ns_mix);
     helperToXmlAddAttribute(writer, "channel", d->channelName);
     if (type() == Result)
         helperToXmlAddAttribute(writer, "jid", d->jid);
diff --git a/src/base/QXmppMucIq.cpp b/src/base/QXmppMucIq.cpp
index df17c34c..7120536c 100644
--- a/src/base/QXmppMucIq.cpp
+++ b/src/base/QXmppMucIq.cpp
@@ -277,7 +277,7 @@ void QXmppMucAdminIq::parseElementFromChild(const QDomElement &element)
 void QXmppMucAdminIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("query");
-    writer->writeAttribute("xmlns", ns_muc_admin);
+    writer->writeDefaultNamespace(ns_muc_admin);
     for (const QXmppMucItem &item : m_items)
         item.toXml(writer);
     writer->writeEndElement();
@@ -316,7 +316,7 @@ void QXmppMucOwnerIq::parseElementFromChild(const QDomElement &element)
 void QXmppMucOwnerIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("query");
-    writer->writeAttribute("xmlns", ns_muc_owner);
+    writer->writeDefaultNamespace(ns_muc_owner);
     m_form.toXml(writer);
     writer->writeEndElement();
 }
diff --git a/src/base/QXmppNonSASLAuth.cpp b/src/base/QXmppNonSASLAuth.cpp
index 29337e5e..aa6f8791 100644
--- a/src/base/QXmppNonSASLAuth.cpp
+++ b/src/base/QXmppNonSASLAuth.cpp
@@ -93,7 +93,7 @@ void QXmppNonSASLAuthIq::parseElementFromChild(const QDomElement &element)
 void QXmppNonSASLAuthIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("query");
-    writer->writeAttribute("xmlns", ns_auth);
+    writer->writeDefaultNamespace(ns_auth);
     if (!m_username.isEmpty())
         writer->writeTextElement("username", m_username);
     if (!m_digest.isEmpty())
diff --git a/src/base/QXmppPingIq.cpp b/src/base/QXmppPingIq.cpp
index c9f88f89..bbec9dca 100644
--- a/src/base/QXmppPingIq.cpp
+++ b/src/base/QXmppPingIq.cpp
@@ -41,7 +41,7 @@ bool QXmppPingIq::isPingIq(const QDomElement &element)
 void QXmppPingIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("ping");
-    writer->writeAttribute("xmlns", ns_ping);
+    writer->writeDefaultNamespace(ns_ping);
     writer->writeEndElement();
 }
 
diff --git a/src/base/QXmppPresence.cpp b/src/base/QXmppPresence.cpp
index 986f3508..f0353b8d 100644
--- a/src/base/QXmppPresence.cpp
+++ b/src/base/QXmppPresence.cpp
@@ -490,7 +490,7 @@ void QXmppPresence::toXml(QXmlStreamWriter *xmlWriter) const
     // XEP-0045: Multi-User Chat
     if (d->mucSupported) {
         xmlWriter->writeStartElement(QStringLiteral("x"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_muc);
+        xmlWriter->writeDefaultNamespace(ns_muc);
         if (!d->mucPassword.isEmpty())
             xmlWriter->writeTextElement(QStringLiteral("password"), d->mucPassword);
         xmlWriter->writeEndElement();
@@ -498,7 +498,7 @@ void QXmppPresence::toXml(QXmlStreamWriter *xmlWriter) const
 
     if (!d->mucItem.isNull() || !d->mucStatusCodes.isEmpty()) {
         xmlWriter->writeStartElement(QStringLiteral("x"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_muc_user);
+        xmlWriter->writeDefaultNamespace(ns_muc_user);
         if (!d->mucItem.isNull())
             d->mucItem.toXml(xmlWriter);
         for (const auto code : d->mucStatusCodes) {
@@ -514,7 +514,7 @@ void QXmppPresence::toXml(QXmlStreamWriter *xmlWriter) const
             !d->capabilityVer.isEmpty() &&
             !d->capabilityHash.isEmpty()) {
         xmlWriter->writeStartElement(QStringLiteral("c"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_capabilities);
+        xmlWriter->writeDefaultNamespace(ns_capabilities);
         helperToXmlAddAttribute(xmlWriter, QStringLiteral("hash"), d->capabilityHash);
         helperToXmlAddAttribute(xmlWriter, QStringLiteral("node"), d->capabilityNode);
         helperToXmlAddAttribute(xmlWriter, QStringLiteral("ver"), d->capabilityVer.toBase64());
@@ -524,7 +524,7 @@ void QXmppPresence::toXml(QXmlStreamWriter *xmlWriter) const
     // XEP-0153: vCard-Based Avatars
     if (d->vCardUpdateType != VCardUpdateNone) {
         xmlWriter->writeStartElement(QStringLiteral("x"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_vcard_update);
+        xmlWriter->writeDefaultNamespace(ns_vcard_update);
         switch(d->vCardUpdateType) {
         case VCardUpdateNoPhoto:
             xmlWriter->writeEmptyElement(QStringLiteral("photo"));
@@ -541,7 +541,7 @@ void QXmppPresence::toXml(QXmlStreamWriter *xmlWriter) const
     // XEP-0319: Last User Interaction in Presence
     if (!d->lastUserInteraction.isNull() && d->lastUserInteraction.isValid()) {
         xmlWriter->writeStartElement(QStringLiteral("idle"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_idle);
+        xmlWriter->writeDefaultNamespace(ns_idle);
         helperToXmlAddAttribute(xmlWriter, QStringLiteral("since"), QXmppUtils::datetimeToString(d->lastUserInteraction));
         xmlWriter->writeEndElement();
     }
@@ -549,7 +549,7 @@ void QXmppPresence::toXml(QXmlStreamWriter *xmlWriter) const
     // XEP-0405: Mediated Information eXchange (MIX): Participant Server Requirements
     if (!d->mixUserJid.isEmpty() || !d->mixUserNick.isEmpty()) {
         xmlWriter->writeStartElement(QStringLiteral("mix"));
-        xmlWriter->writeAttribute(QStringLiteral("xmlns"), ns_mix_presence);
+        xmlWriter->writeDefaultNamespace(ns_mix_presence);
         if (!d->mixUserJid.isEmpty())
             helperToXmlAddTextElement(xmlWriter, QStringLiteral("jid"), d->mixUserJid);
         if (!d->mixUserNick.isEmpty())
diff --git a/src/base/QXmppPubSubIq.cpp b/src/base/QXmppPubSubIq.cpp
index 1c984c1b..ea96903b 100644
--- a/src/base/QXmppPubSubIq.cpp
+++ b/src/base/QXmppPubSubIq.cpp
@@ -198,7 +198,7 @@ void QXmppPubSubIq::parseElementFromChild(const QDomElement &element)
 void QXmppPubSubIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("pubsub");
-    writer->writeAttribute("xmlns", ns_pubsub);
+    writer->writeDefaultNamespace(ns_pubsub);
 
     // write query type
     writer->writeStartElement(PUBSUB_QUERIES.at(d->queryType));
diff --git a/src/base/QXmppRegisterIq.cpp b/src/base/QXmppRegisterIq.cpp
index 77d759c8..79231c9a 100644
--- a/src/base/QXmppRegisterIq.cpp
+++ b/src/base/QXmppRegisterIq.cpp
@@ -219,7 +219,7 @@ void QXmppRegisterIq::parseElementFromChild(const QDomElement &element)
 void QXmppRegisterIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("query");
-    writer->writeAttribute("xmlns", ns_register);
+    writer->writeDefaultNamespace(ns_register);
 
     if (!d->instructions.isEmpty())
         writer->writeTextElement("instructions", d->instructions);
diff --git a/src/base/QXmppResultSet.cpp b/src/base/QXmppResultSet.cpp
index a08b0e87..fc4fd88c 100644
--- a/src/base/QXmppResultSet.cpp
+++ b/src/base/QXmppResultSet.cpp
@@ -134,7 +134,7 @@ void QXmppResultSetQuery::toXml(QXmlStreamWriter* writer) const
     if (isNull())
         return;
     writer->writeStartElement("set");
-    writer->writeAttribute("xmlns", ns_rsm);
+    writer->writeDefaultNamespace(ns_rsm);
     if (m_max >= 0)
         helperToXmlAddTextElement(writer, "max", QString::number(m_max));
     if (!m_after.isNull())
@@ -247,7 +247,7 @@ void QXmppResultSetReply::toXml(QXmlStreamWriter* writer) const
     if (isNull())
         return;
     writer->writeStartElement("set");
-    writer->writeAttribute("xmlns", ns_rsm);
+    writer->writeDefaultNamespace(ns_rsm);
     if (!m_first.isNull() || m_index >= 0) {
         writer->writeStartElement("first");
         if (m_index >= 0)
diff --git a/src/base/QXmppRosterIq.cpp b/src/base/QXmppRosterIq.cpp
index 565b985f..01e0956d 100644
--- a/src/base/QXmppRosterIq.cpp
+++ b/src/base/QXmppRosterIq.cpp
@@ -107,7 +107,7 @@ void QXmppRosterIq::parseElementFromChild(const QDomElement &element)
 void QXmppRosterIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("query");
-    writer->writeAttribute( "xmlns", ns_roster);
+    writer->writeDefaultNamespace(ns_roster);
 
     // XEP-0237 roster versioning - If the server does not advertise support for roster versioning, the client MUST NOT include the 'ver' attribute.
     if(!version().isEmpty())
diff --git a/src/base/QXmppRpcIq.cpp b/src/base/QXmppRpcIq.cpp
index ed8a8ea1..b69aef48 100644
--- a/src/base/QXmppRpcIq.cpp
+++ b/src/base/QXmppRpcIq.cpp
@@ -322,7 +322,7 @@ void QXmppRpcResponseIq::parseElementFromChild(const QDomElement &element)
 void QXmppRpcResponseIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("query");
-    writer->writeAttribute("xmlns", ns_rpc);
+    writer->writeDefaultNamespace(ns_rpc);
 
     writer->writeStartElement("methodResponse");
     if (m_faultCode)
@@ -425,7 +425,7 @@ void QXmppRpcInvokeIq::parseElementFromChild(const QDomElement &element)
 void QXmppRpcInvokeIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("query");
-    writer->writeAttribute("xmlns", ns_rpc);
+    writer->writeDefaultNamespace(ns_rpc);
 
     writer->writeStartElement("methodCall");
     writer->writeTextElement("methodName", m_method);
diff --git a/src/base/QXmppSasl.cpp b/src/base/QXmppSasl.cpp
index 213fcc0b..3f70b093 100644
--- a/src/base/QXmppSasl.cpp
+++ b/src/base/QXmppSasl.cpp
@@ -138,7 +138,7 @@ void QXmppSaslAuth::parse(const QDomElement &element)
 void QXmppSaslAuth::toXml(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("auth");
-    writer->writeAttribute("xmlns", ns_xmpp_sasl);
+    writer->writeDefaultNamespace(ns_xmpp_sasl);
     writer->writeAttribute("mechanism", m_mechanism);
     if (!m_value.isEmpty())
         writer->writeCharacters(m_value.toBase64());
@@ -168,7 +168,7 @@ void QXmppSaslChallenge::parse(const QDomElement &element)
 void QXmppSaslChallenge::toXml(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("challenge");
-    writer->writeAttribute("xmlns", ns_xmpp_sasl);
+    writer->writeDefaultNamespace(ns_xmpp_sasl);
     if (!m_value.isEmpty())
         writer->writeCharacters(m_value.toBase64());
     writer->writeEndElement();
@@ -197,7 +197,7 @@ void QXmppSaslFailure::parse(const QDomElement &element)
 void QXmppSaslFailure::toXml(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("failure");
-    writer->writeAttribute("xmlns", ns_xmpp_sasl);
+    writer->writeDefaultNamespace(ns_xmpp_sasl);
     if (!m_condition.isEmpty())
         writer->writeEmptyElement(m_condition);
     writer->writeEndElement();
@@ -226,7 +226,7 @@ void QXmppSaslResponse::parse(const QDomElement &element)
 void QXmppSaslResponse::toXml(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("response");
-    writer->writeAttribute("xmlns", ns_xmpp_sasl);
+    writer->writeDefaultNamespace(ns_xmpp_sasl);
     if (!m_value.isEmpty())
         writer->writeCharacters(m_value.toBase64());
     writer->writeEndElement();
@@ -244,7 +244,7 @@ void QXmppSaslSuccess::parse(const QDomElement &element)
 void QXmppSaslSuccess::toXml(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("success");
-    writer->writeAttribute("xmlns", ns_xmpp_sasl);
+    writer->writeDefaultNamespace(ns_xmpp_sasl);
     writer->writeEndElement();
 }
 
diff --git a/src/base/QXmppSessionIq.cpp b/src/base/QXmppSessionIq.cpp
index 3221ca85..4916fef5 100644
--- a/src/base/QXmppSessionIq.cpp
+++ b/src/base/QXmppSessionIq.cpp
@@ -39,7 +39,7 @@ bool QXmppSessionIq::isSessionIq(const QDomElement &element)
 void QXmppSessionIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("session");;
-    writer->writeAttribute("xmlns", ns_session);
+    writer->writeDefaultNamespace(ns_session);
     writer->writeEndElement();
 }
 /// \endcond
diff --git a/src/base/QXmppStanza.cpp b/src/base/QXmppStanza.cpp
index f875f17b..002ef65a 100644
--- a/src/base/QXmppStanza.cpp
+++ b/src/base/QXmppStanza.cpp
@@ -403,13 +403,13 @@ void QXmppStanza::Error::toXml(QXmlStreamWriter *writer) const
 
     if (!cond.isEmpty()) {
         writer->writeStartElement(cond);
-        writer->writeAttribute("xmlns", ns_stanza);
+        writer->writeDefaultNamespace(ns_stanza);
         writer->writeEndElement();
     }
     if (!d->text.isEmpty()) {
         writer->writeStartElement("text");
         writer->writeAttribute("xml:lang", "en");
-        writer->writeAttribute("xmlns", ns_stanza);
+        writer->writeDefaultNamespace(ns_stanza);
         writer->writeCharacters(d->text);
         writer->writeEndElement();
     }
@@ -417,13 +417,13 @@ void QXmppStanza::Error::toXml(QXmlStreamWriter *writer) const
     // XEP-0363: HTTP File Upload
     if (d->fileTooLarge) {
         writer->writeStartElement("file-too-large");
-        writer->writeAttribute("xmlns", ns_http_upload);
+        writer->writeDefaultNamespace(ns_http_upload);
         helperToXmlAddTextElement(writer, "max-file-size",
                                   QString::number(d->maxFileSize));
         writer->writeEndElement();
     } else if (!d->retryDate.isNull() && d->retryDate.isValid()) {
         writer->writeStartElement("retry");
-        writer->writeAttribute("xmlns", ns_http_upload);
+        writer->writeDefaultNamespace(ns_http_upload);
         writer->writeAttribute("stamp",
                                QXmppUtils::datetimeToString(d->retryDate));
         writer->writeEndElement();
@@ -636,7 +636,7 @@ void QXmppStanza::extensionsToXml(QXmlStreamWriter *xmlWriter) const
     // XEP-0033: Extended Stanza Addressing
     if (!d->extendedAddresses.isEmpty()) {
         xmlWriter->writeStartElement("addresses");
-        xmlWriter->writeAttribute("xmlns", ns_extended_addressing);
+        xmlWriter->writeDefaultNamespace(ns_extended_addressing);
         for (const auto &address : d->extendedAddresses)
             address.toXml(xmlWriter);
         xmlWriter->writeEndElement();
diff --git a/src/base/QXmppStartTlsPacket.cpp b/src/base/QXmppStartTlsPacket.cpp
index f3c7edca..ea5feef9 100644
--- a/src/base/QXmppStartTlsPacket.cpp
+++ b/src/base/QXmppStartTlsPacket.cpp
@@ -71,7 +71,7 @@ void QXmppStartTlsPacket::parse(const QDomElement &element)
 void QXmppStartTlsPacket::toXml(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement(STARTTLS_TYPES.at(int(m_type)));
-    writer->writeAttribute(QStringLiteral("xmlns"), ns_tls);
+    writer->writeDefaultNamespace(ns_tls);
     writer->writeEndElement();
 }
 /// \endcond
diff --git a/src/base/QXmppStreamFeatures.cpp b/src/base/QXmppStreamFeatures.cpp
index 84cdc965..992cf309 100644
--- a/src/base/QXmppStreamFeatures.cpp
+++ b/src/base/QXmppStreamFeatures.cpp
@@ -189,7 +189,7 @@ static void writeFeature(QXmlStreamWriter *writer, const char *tagName, const ch
     if (mode != QXmppStreamFeatures::Disabled)
     {
         writer->writeStartElement(tagName);
-        writer->writeAttribute("xmlns", tagNs);
+        writer->writeDefaultNamespace(tagNs);
         if (mode == QXmppStreamFeatures::Required)
             writer->writeEmptyElement("required");
         writer->writeEndElement();
@@ -210,7 +210,7 @@ void QXmppStreamFeatures::toXml(QXmlStreamWriter *writer) const
     if (!m_compressionMethods.isEmpty())
     {
         writer->writeStartElement("compression");
-        writer->writeAttribute("xmlns", ns_compressFeature);
+        writer->writeDefaultNamespace(ns_compressFeature);
         for (const auto &method : m_compressionMethods)
             writer->writeTextElement("method", method);
         writer->writeEndElement();
@@ -218,7 +218,7 @@ void QXmppStreamFeatures::toXml(QXmlStreamWriter *writer) const
     if (!m_authMechanisms.isEmpty())
     {
         writer->writeStartElement("mechanisms");
-        writer->writeAttribute("xmlns", ns_sasl);
+        writer->writeDefaultNamespace(ns_sasl);
         for (const auto &mechanism : m_authMechanisms)
             writer->writeTextElement("mechanism",  mechanism);
         writer->writeEndElement();
diff --git a/src/base/QXmppStreamInitiationIq.cpp b/src/base/QXmppStreamInitiationIq.cpp
index 5078f411..87067b65 100644
--- a/src/base/QXmppStreamInitiationIq.cpp
+++ b/src/base/QXmppStreamInitiationIq.cpp
@@ -109,7 +109,7 @@ void QXmppStreamInitiationIq::parseElementFromChild(const QDomElement &element)
 void QXmppStreamInitiationIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("si");
-    writer->writeAttribute("xmlns", ns_stream_initiation);
+    writer->writeDefaultNamespace(ns_stream_initiation);
     helperToXmlAddAttribute(writer, "id", m_siId);
     helperToXmlAddAttribute(writer, "mime-type", m_mimeType);
     if (m_profile == FileTransfer)
@@ -118,7 +118,7 @@ void QXmppStreamInitiationIq::toXmlElementFromChild(QXmlStreamWriter *writer) co
         m_fileInfo.toXml(writer);
     if (!m_featureForm.isNull()) {
         writer->writeStartElement("feature");
-        writer->writeAttribute("xmlns", ns_feature_negotiation);
+        writer->writeDefaultNamespace(ns_feature_negotiation);
         m_featureForm.toXml(writer);
         writer->writeEndElement();
     }
diff --git a/src/base/QXmppStreamManagement.cpp b/src/base/QXmppStreamManagement.cpp
index 841184de..1e9a96fc 100644
--- a/src/base/QXmppStreamManagement.cpp
+++ b/src/base/QXmppStreamManagement.cpp
@@ -67,7 +67,7 @@ void QXmppStreamManagementEnable::parse(const QDomElement &element)
 void QXmppStreamManagementEnable::toXml(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("enable");
-    writer->writeAttribute("xmlns", ns_stream_management);
+    writer->writeDefaultNamespace(ns_stream_management);
     if (m_resume)
         writer->writeAttribute("resume", "true");
     if (m_max > 0)
@@ -137,7 +137,7 @@ void QXmppStreamManagementEnabled::parse(const QDomElement &element)
 void QXmppStreamManagementEnabled::toXml(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("enable");
-    writer->writeAttribute("xmlns", ns_stream_management);
+    writer->writeDefaultNamespace(ns_stream_management);
     if (m_resume)
         writer->writeAttribute("resume", "true");
     if (m_max > 0)
@@ -271,7 +271,7 @@ void QXmppStreamManagementFailed::toXml(QXmlStreamWriter *writer) const
     QString errorString = strFromCondition(m_error);
 
     writer->writeStartElement("failed");
-    writer->writeAttribute("xmlns", ns_stream_management);
+    writer->writeDefaultNamespace(ns_stream_management);
     writer->writeStartElement(errorString, ns_stanza);
     writer->writeEndElement();
     writer->writeEndElement();
@@ -300,7 +300,7 @@ void QXmppStreamManagementAck::parse(const QDomElement &element)
 void QXmppStreamManagementAck::toXml(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("a");
-    writer->writeAttribute("xmlns", ns_stream_management);
+    writer->writeDefaultNamespace(ns_stream_management);
     writer->writeAttribute("h", QString::number(m_seqNo));
     writer->writeEndElement();
 }
@@ -320,6 +320,6 @@ bool QXmppStreamManagementReq::isStreamManagementReq(const QDomElement &element)
 void QXmppStreamManagementReq::toXml(QXmlStreamWriter *writer)
 {
     writer->writeStartElement("r");
-    writer->writeAttribute("xmlns", ns_stream_management);
+    writer->writeDefaultNamespace(ns_stream_management);
     writer->writeEndElement();
 }
diff --git a/src/base/QXmppVCardIq.cpp b/src/base/QXmppVCardIq.cpp
index d885ab04..839229bc 100644
--- a/src/base/QXmppVCardIq.cpp
+++ b/src/base/QXmppVCardIq.cpp
@@ -1008,7 +1008,7 @@ void QXmppVCardIq::parseElementFromChild(const QDomElement& nodeRecv)
 void QXmppVCardIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("vCard");
-    writer->writeAttribute("xmlns", ns_vcard);
+    writer->writeDefaultNamespace(ns_vcard);
     for (const QXmppVCardAddress &address : d->addresses)
         address.toXml(writer);
     if (d->birthday.isValid())
diff --git a/src/base/QXmppVersionIq.cpp b/src/base/QXmppVersionIq.cpp
index 4b7cded9..7d41aebd 100644
--- a/src/base/QXmppVersionIq.cpp
+++ b/src/base/QXmppVersionIq.cpp
@@ -96,7 +96,7 @@ void QXmppVersionIq::parseElementFromChild(const QDomElement &element)
 void QXmppVersionIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("query");
-    writer->writeAttribute("xmlns", ns_version);
+    writer->writeDefaultNamespace(ns_version);
 
     if (!m_name.isEmpty())
         helperToXmlAddTextElement(writer, "name", m_name);
diff --git a/src/client/QXmppBookmarkManager.cpp b/src/client/QXmppBookmarkManager.cpp
index 0cf993c3..246d2437 100644
--- a/src/client/QXmppBookmarkManager.cpp
+++ b/src/client/QXmppBookmarkManager.cpp
@@ -77,7 +77,7 @@ void QXmppPrivateStorageIq::parseElementFromChild(const QDomElement &element)
 void QXmppPrivateStorageIq::toXmlElementFromChild(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("query");
-    writer->writeAttribute("xmlns", ns_private);
+    writer->writeDefaultNamespace(ns_private);
     m_bookmarks.toXml(writer);
     writer->writeEndElement();
 }
diff --git a/src/client/QXmppTransferManager.cpp b/src/client/QXmppTransferManager.cpp
index cdcd8689..3621ba6f 100644
--- a/src/client/QXmppTransferManager.cpp
+++ b/src/client/QXmppTransferManager.cpp
@@ -171,7 +171,7 @@ void QXmppTransferFileInfo::parse(const QDomElement &element)
 void QXmppTransferFileInfo::toXml(QXmlStreamWriter *writer) const
 {
     writer->writeStartElement("file");
-    writer->writeAttribute("xmlns", ns_stream_initiation_file_transfer);
+    writer->writeDefaultNamespace(ns_stream_initiation_file_transfer);
     if (d->date.isValid())
         writer->writeAttribute("date", QXmppUtils::datetimeToString(d->date));
     if (!d->hash.isEmpty())
diff --git a/src/server/QXmppServer.cpp b/src/server/QXmppServer.cpp
index 2cf25362..49a5d6fe 100644
--- a/src/server/QXmppServer.cpp
+++ b/src/server/QXmppServer.cpp
@@ -48,7 +48,7 @@ static void helperToXmlAddDomElement(QXmlStreamWriter* stream, const QDomElement
     /* attributes */
     QString xmlns = element.namespaceURI();
     if (!xmlns.isEmpty() && !omitNamespaces.contains(xmlns))
-        stream->writeAttribute("xmlns", xmlns);
+        stream->writeDefaultNamespace(xmlns);
     QDomNamedNodeMap attrs = element.attributes();
     for (int i = 0; i < attrs.size(); i++)
     {