diff --git a/src/gui/text/qtextdocument_p.cpp b/src/gui/text/qtextdocument_p.cpp
index 0180fbb6ff..0718300d37 100644
--- a/src/gui/text/qtextdocument_p.cpp
+++ b/src/gui/text/qtextdocument_p.cpp
@@ -1305,10 +1305,14 @@ void QTextDocumentPrivate::adjustDocumentChangesAndCursors(int from, int addedOr
 QString QTextDocumentPrivate::plainText() const
 {
     QString result;
-    result.reserve(length());
-    const auto view = QStringView(text);
-    for (auto f : *this)
-        result += view.sliced(f->stringPosition, f->size_array[0]);
+    result.resize(length());
+    const QChar *text_unicode = text.unicode();
+    QChar *data = result.data();
+    for (QTextDocumentPrivate::FragmentIterator it = begin(); it != end(); ++it) {
+        const QTextFragmentData *f = *it;
+        ::memcpy(data, text_unicode + f->stringPosition, f->size_array[0] * sizeof(QChar));
+        data += f->size_array[0];
+    }
     // remove trailing block separator
     result.chop(1);
     return result;