diff --git a/src/xml/dom/qdomhelpers.cpp b/src/xml/dom/qdomhelpers.cpp
index 39c7dcd360d..b58d2f7ae94 100644
--- a/src/xml/dom/qdomhelpers.cpp
+++ b/src/xml/dom/qdomhelpers.cpp
@@ -52,6 +52,35 @@ bool QDomBuilder::startDTD(const QString &name, const QString &publicId, const Q
     return true;
 }
 
+QString QDomBuilder::dtdInternalSubset(const QString &dtd)
+{
+    // https://www.w3.org/TR/xml/#NT-intSubset
+    // doctypedecl: '<!DOCTYPE' S Name (S ExternalID)? S? ('[' intSubset ']' S?)? '>'
+    const QString &name = doc->doctype()->name;
+    QStringView tmp = QStringView(dtd).sliced(dtd.indexOf(name) + name.size());
+
+    const QString &publicId = doc->doctype()->publicId;
+    if (!publicId.isEmpty())
+        tmp = tmp.sliced(tmp.indexOf(publicId) + publicId.size());
+
+    const QString &systemId = doc->doctype()->systemId;
+    if (!systemId.isEmpty())
+        tmp = tmp.sliced(tmp.indexOf(systemId) + systemId.size());
+
+    const qsizetype obra = tmp.indexOf(u'[');
+    const qsizetype cbra = tmp.lastIndexOf(u']');
+    if (obra >= 0 && cbra >= 0)
+        return tmp.left(cbra).sliced(obra + 1).toString();
+
+    return QString();
+}
+
+bool QDomBuilder::parseDTD(const QString &dtd)
+{
+    doc->doctype()->internalSubset = dtdInternalSubset(dtd);
+    return true;
+}
+
 bool QDomBuilder::startElement(const QString &nsURI, const QString &qName,
                                const QXmlStreamAttributes &atts)
 {
@@ -272,6 +301,8 @@ bool QDomParser::parseProlog()
                         QDomParser::tr("Error occurred while processing document type declaration"));
                 return false;
             }
+            if (!domBuilder.parseDTD(reader->text().toString()))
+                return false;
             if (!parseMarkupDecl())
                 return false;
             break;
diff --git a/src/xml/dom/qdomhelpers_p.h b/src/xml/dom/qdomhelpers_p.h
index f2a0a79c3a0..81de6e2e801 100644
--- a/src/xml/dom/qdomhelpers_p.h
+++ b/src/xml/dom/qdomhelpers_p.h
@@ -45,6 +45,7 @@ class QDomBuilder
     bool startEntity(const QString &name);
     bool endEntity();
     bool startDTD(const QString &name, const QString &publicId, const QString &systemId);
+    bool parseDTD(const QString &dtd);
     bool comment(const QString &characters);
     bool externalEntityDecl(const QString &name, const QString &publicId, const QString &systemId);
     bool notationDecl(const QString &name, const QString &publicId, const QString &systemId);
@@ -61,6 +62,8 @@ class QDomBuilder
     int errorColumn;
 
 private:
+    QString dtdInternalSubset(const QString &dtd);
+
     QDomDocumentPrivate *doc;
     QDomNodePrivate *node;
     QXmlStreamReader *reader;
diff --git a/tests/auto/xml/dom/qdom/tst_qdom.cpp b/tests/auto/xml/dom/qdom/tst_qdom.cpp
index f05020f61ca..0736e158fcc 100644
--- a/tests/auto/xml/dom/qdom/tst_qdom.cpp
+++ b/tests/auto/xml/dom/qdom/tst_qdom.cpp
@@ -97,6 +97,8 @@ private slots:
     void cloneDTD_QTBUG8398() const;
     void DTDNotationDecl();
     void DTDEntityDecl();
+    void DTDInternalSubset() const;
+    void DTDInternalSubset_data() const;
     void QTBUG49113_dontCrashWithNegativeIndex() const;
 
     void cleanupTestCase() const;
@@ -2044,5 +2046,69 @@ void tst_QDom::QTBUG49113_dontCrashWithNegativeIndex() const
     QVERIFY(node.isNull());
 }
 
+void tst_QDom::DTDInternalSubset() const
+{
+    QFETCH( QString, doc );
+    QFETCH( QString, internalSubset );
+    QXmlStreamReader reader(doc);
+    QDomDocument document;
+    QVERIFY(document.setContent(&reader, true));
+
+    QCOMPARE(document.doctype().internalSubset(), internalSubset);
+}
+
+void tst_QDom::DTDInternalSubset_data() const
+{
+    QTest::addColumn<QString>("doc");
+    QTest::addColumn<QString>("internalSubset");
+
+    QTest::newRow("data1") << "<?xml version='1.0'?>\n"
+                              "<!DOCTYPE note SYSTEM '/[abcd].dtd'>\n"
+                              "<note/>\n"
+                           << "" ;
+
+    QTest::newRow("data2") << "<?xml version='1.0'?>\n"
+                              "<!DOCTYPE note PUBLIC '-/freedesktop' 'https://[abcd].dtd'>\n"
+                              "<note/>\n"
+                           << "" ;
+
+    const QString internalSubset0(
+                "<!-- open brackets comment [ -->\n"
+                "<!-- colse brackets comment ] -->\n"
+                );
+    QTest::newRow("data3") << "<?xml version='1.0'?>\n"
+                              "<!DOCTYPE note ["
+                              + internalSubset0 +
+                              "]>\n"
+                              "<note/>\n"
+                           << internalSubset0;
+
+    const QString internalSubset1(
+                "<!ENTITY obra '['>\n"
+                "<!ENTITY cbra ']'>\n"
+                );
+    QTest::newRow("data4") << "<?xml version='1.0'?>\n"
+                              "<!DOCTYPE note ["
+                              + internalSubset1 +
+                              "]>\n"
+                              "<note/>\n"
+                           << internalSubset1;
+
+    QTest::newRow("data5") << "<?xml version='1.0'?>\n"
+          "<!DOCTYPE note  PUBLIC '-/freedesktop' 'https://[abcd].dtd' ["
+          + internalSubset0
+          + "]>\n"
+          "<note/>\n"
+       << internalSubset0;
+
+    QTest::newRow("data6") << "<?xml version='1.0'?>\n"
+          "<!DOCTYPE note  PUBLIC '-/freedesktop' "
+            "'2001:db8:130F:0000:0000:09C0:876A:130B://[abcd].dtd' ["
+          + internalSubset0
+          + "]>\n"
+          "<note/>\n"
+       << internalSubset0;
+}
+
 QTEST_MAIN(tst_QDom)
 #include "tst_qdom.moc"