diff --git a/src/plugins/platforms/windows/qwindowsdialoghelpers.cpp b/src/plugins/platforms/windows/qwindowsdialoghelpers.cpp
index ca5b90b4290..993dff51290 100644
--- a/src/plugins/platforms/windows/qwindowsdialoghelpers.cpp
+++ b/src/plugins/platforms/windows/qwindowsdialoghelpers.cpp
@@ -1325,7 +1325,7 @@ void QWindowsNativeFileDialogBase::setLabelText(QFileDialogOptions::DialogLabel
 static inline bool isClsid(const QString &s)
 {
     // detect "374DE290-123F-4565-9164-39C4925E467B".
-   static const QRegularExpression pattern(QLatin1String("[0-9A-Fa-f]{8}-[0-9A-Fa-f]{4}-[0-9A-Fa-f]{4}-[0-9A-Fa-f]{4}-[0-9A-Fa-f]{8}"));
+   static const QRegularExpression pattern(QLatin1String("\\A[0-9A-Fa-f]{8}-[0-9A-Fa-f]{4}-[0-9A-Fa-f]{4}-[0-9A-Fa-f]{4}-[0-9A-Fa-f]{12}\\z"));
    Q_ASSERT(pattern.isValid());
    return pattern.match(s).hasMatch();
 }