2 files changed, 10 insertions, 5 deletions
diff --git a/src/corelib/serialization/qxmlstream.cpp b/src/corelib/serialization/qxmlstream.cpp
index e68544b1cf5..b32d32c1a41 100644
--- a/src/corelib/serialization/qxmlstream.cpp
+++ b/src/corelib/serialization/qxmlstream.cpp
@@ -3069,13 +3069,11 @@ void QXmlStreamWriterPrivate::doWriteToDevice(QStringView s)
     while (!s.isEmpty()) {
         const qsizetype chunkSize = std::min(s.size(), MaxChunkSize);
         char *end = QUtf8::convertFromUnicode(buffer, s.first(chunkSize), &state);
-        if (state.remainingChars > 0) {
-            hasEncodingError = true;
-            return;
-        }
         doWriteToDevice(QUtf8StringView{buffer, end});
         s = s.sliced(chunkSize);
     }
+    if (state.remainingChars > 0)
+        hasEncodingError = true;
 }
 
 void QXmlStreamWriterPrivate::doWriteToDevice(QUtf8StringView s)
diff --git a/tests/auto/corelib/serialization/qxmlstream/tst_qxmlstream.cpp b/tests/auto/corelib/serialization/qxmlstream/tst_qxmlstream.cpp
index b91182d3097..a91a9bc752f 100644
--- a/tests/auto/corelib/serialization/qxmlstream/tst_qxmlstream.cpp
+++ b/tests/auto/corelib/serialization/qxmlstream/tst_qxmlstream.cpp
@@ -1695,16 +1695,23 @@ void tst_QXmlStream::readBack() const
 {
     QFETCH(const int, plane);
 
+    constexpr qsizetype MaxChunkSizeWhenEncoding = 512; // from qxmlstream.cpp
     QBuffer buffer;
+    QString text = QString(513, 'a'); // one longer than the internal conversion buffer
 
     for (char16_t i = 0; i < (std::numeric_limits<char16_t>::max)(); ++i) {
 
         const char32_t c = (plane << 16) + i;
 
+        // end chunk in invalid character, split surrogates:
+        const auto pair = QChar::fromUcs4(c);
+        text.resize(MaxChunkSizeWhenEncoding + 1 - pair.size());
+        text += pair;
+
         QVERIFY(buffer.open(QIODevice::WriteOnly|QIODevice::Truncate));
         QXmlStreamWriter writer(&buffer);
         writer.writeStartDocument();
-        writer.writeTextElement("a", c);
+        writer.writeTextElement("a", text);
         writer.writeEndDocument();
         buffer.close();