diff --git a/src/corelib/text/qstringconverter_p.h b/src/corelib/text/qstringconverter_p.h
index 5929fe08000..e8012726467 100644
--- a/src/corelib/text/qstringconverter_p.h
+++ b/src/corelib/text/qstringconverter_p.h
@@ -306,6 +306,7 @@ struct Q_CORE_EXPORT QLocal8Bit
     static int checkUtf8();
     static bool isUtf8()
     {
+        Q_CONSTINIT
         static QBasicAtomicInteger<qint8> result = { 0 };
         int r = result.loadRelaxed();
         if (r == 0) {