diff --git a/src/gui/text/qtextengine.cpp b/src/gui/text/qtextengine.cpp
index d0c2779a65..17a91f5a6a 100644
--- a/src/gui/text/qtextengine.cpp
+++ b/src/gui/text/qtextengine.cpp
@@ -1635,8 +1635,14 @@ void QTextEngine::itemize() const
             if (analysis->bidiLevel % 2)
                 --analysis->bidiLevel;
             analysis->flags = QScriptAnalysis::LineOrParagraphSeparator;
-            if (option.flags() & QTextOption::ShowLineAndParagraphSeparators)
+            if (option.flags() & QTextOption::ShowLineAndParagraphSeparators) {
+                const int offset = uc - string;
+                layoutData->string.detach();
+                string = reinterpret_cast<const ushort *>(layoutData->string.unicode());
+                uc = string + offset;
+                e = uc + length;
                 *const_cast<ushort*>(uc) = 0x21B5; // visual line separator
+            }
             break;
         case QChar::Tabulation:
             analysis->flags = QScriptAnalysis::Tab;
diff --git a/tests/auto/gui/text/qtextlayout/tst_qtextlayout.cpp b/tests/auto/gui/text/qtextlayout/tst_qtextlayout.cpp
index de0c2d6dbe..e778232461 100644
--- a/tests/auto/gui/text/qtextlayout/tst_qtextlayout.cpp
+++ b/tests/auto/gui/text/qtextlayout/tst_qtextlayout.cpp
@@ -142,6 +142,7 @@ private slots:
     void xToCursorForLigatures();
     void cursorInNonStopChars();
     void nbsp();
+    void noModificationOfInputString();
 
 private:
     QFont testFont;
@@ -2176,5 +2177,37 @@ void tst_QTextLayout::layoutWithCustomTabStops()
     QVERIFY(longWidth > shortWidth);
 }
 
+void tst_QTextLayout::noModificationOfInputString()
+{
+    QString s = QString(QChar(QChar::LineSeparator));
+    {
+        QTextLayout layout;
+        layout.setText(s);
+
+        layout.beginLayout();
+        layout.createLine();
+        layout.endLayout();
+
+        QCOMPARE(s.size(), 1);
+        QCOMPARE(s.at(0), QChar(QChar::LineSeparator));
+    }
+
+    {
+        QTextLayout layout;
+        layout.setText(s);
+
+        QTextOption option;
+        option.setFlags(QTextOption::ShowLineAndParagraphSeparators);
+        layout.setTextOption(option);
+
+        layout.beginLayout();
+        layout.createLine();
+        layout.endLayout();
+
+        QCOMPARE(s.size(), 1);
+        QCOMPARE(s.at(0), QChar(QChar::LineSeparator));
+    }
+}
+
 QTEST_MAIN(tst_QTextLayout)
 #include "tst_qtextlayout.moc"