diff --git a/src/plugins/platforms/wayland/qwaylandwindow.cpp b/src/plugins/platforms/wayland/qwaylandwindow.cpp
index ccfcaf933fb..ae26ba04946 100644
--- a/src/plugins/platforms/wayland/qwaylandwindow.cpp
+++ b/src/plugins/platforms/wayland/qwaylandwindow.cpp
@@ -298,8 +298,10 @@ void QWaylandWindow::setWindowTitle(const QString &title)
         const QString formatted = formatWindowTitle(title, separator);
 
         const int libwaylandMaxBufferSize = 4096;
-        // Some parts of the buffer is used for metadata, so subtract 100 to be on the safe side
-        const int maxLength = libwaylandMaxBufferSize - 100;
+        // Some parts of the buffer is used for metadata, so subtract 100 to be on the safe side.
+        // Also, QString is in utf-16, which means that in the worst case each character will be
+        // three bytes when converted to utf-8 (which is what libwayland uses), so divide by three.
+        const int maxLength = libwaylandMaxBufferSize / 3 - 100;
 
         auto truncated = QStringRef(&formatted).left(maxLength);
         if (truncated.length() < formatted.length()) {
diff --git a/tests/auto/wayland/client/tst_client.cpp b/tests/auto/wayland/client/tst_client.cpp
index 08120c8c24f..83b9e6ce0b3 100644
--- a/tests/auto/wayland/client/tst_client.cpp
+++ b/tests/auto/wayland/client/tst_client.cpp
@@ -178,6 +178,7 @@ private slots:
     void hiddenPopupParent();
     void glWindow();
     void longWindowTitle();
+    void longWindowTitleWithUtf16Characters();
 
 private:
     MockCompositor *compositor = nullptr;
@@ -494,6 +495,16 @@ void tst_WaylandClient::longWindowTitle()
     QTRY_VERIFY(compositor->surface());
 }
 
+void tst_WaylandClient::longWindowTitleWithUtf16Characters()
+{
+    QWindow window;
+    QString absurdlyLongTitle = QString("三").repeated(10000);
+    Q_ASSERT(absurdlyLongTitle.length() == 10000); // just making sure the test isn't broken
+    window.setTitle(absurdlyLongTitle);
+    window.show();
+    QTRY_VERIFY(compositor->surface());
+}
+
 int main(int argc, char **argv)
 {
     setenv("XDG_RUNTIME_DIR", ".", 1);