diff --git a/5.15.2/qtbase/src/plugins/styles/mac/qmacstyle_mac.mm b/5.15.2/qtbase/src/plugins/styles/mac/qmacstyle_mac.mm
index d21c276..1038be8 100644
--- a/5.15.2/qtbase/src/plugins/styles/mac/qmacstyle_mac.mm
+++ b/5.15.2/qtbase/src/plugins/styles/mac/qmacstyle_mac.mm
@@ -848,6 +848,8 @@ static QSize qt_aqua_get_known_size(QStyle::ContentsType ct, const QWidget *widg
             return ret;
     }
 
+    const bool isBigSurOrAbove = QOperatingSystemVersion::current() >= QOperatingSystemVersion::MacOSBigSur;
+
     if (ct == QStyle::CT_CustomBase && widg) {
 #if QT_CONFIG(pushbutton)
         if (qobject_cast<const QPushButton *>(widg))
@@ -1042,6 +1044,8 @@ static QSize qt_aqua_get_known_size(QStyle::ContentsType ct, const QWidget *widg
                     w = qt_mac_aqua_get_metric(HSliderHeight);
                     if (sld->tickPosition() != QSlider::NoTicks)
                         w += qt_mac_aqua_get_metric(HSliderTickHeight);
+                    else if (isBigSurOrAbove)
+                        w += 3;
                 } else {
                     w = qt_mac_aqua_get_metric(VSliderWidth);
                     if (sld->tickPosition() != QSlider::NoTicks)