diff --git a/src/plugins/styles/mac/qmacstyle_mac.mm b/src/plugins/styles/mac/qmacstyle_mac.mm
index 4515b2b0ed..12b8e0c2f1 100644
--- a/src/plugins/styles/mac/qmacstyle_mac.mm
+++ b/src/plugins/styles/mac/qmacstyle_mac.mm
@@ -844,6 +844,8 @@ static QSize qt_aqua_get_known_size(QStyle::ContentsType ct, const QStyleOption
             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))
@@ -1024,6 +1026,8 @@ static QSize qt_aqua_get_known_size(QStyle::ContentsType ct, const QStyleOption
                     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)
diff --git a/tests/auto/widgets/styles/qmacstyle/tst_qmacstyle.cpp b/tests/auto/widgets/styles/qmacstyle/tst_qmacstyle.cpp
index e9802cd716..fd784f9ced 100644
--- a/tests/auto/widgets/styles/qmacstyle/tst_qmacstyle.cpp
+++ b/tests/auto/widgets/styles/qmacstyle/tst_qmacstyle.cpp
@@ -83,6 +83,10 @@ private:
 #define SIZE(x, y, z) \
     ((size == QStyleHelper::SizeLarge) ? (x) : (size == QStyleHelper::SizeSmall) ? (y) : (z))
 
+static bool bigSurOrAbove() {
+    return QOperatingSystemVersion::current() >= QOperatingSystemVersion::MacOSBigSur;
+}
+
 void tst_QMacStyle::sizeHints_data()
 {
     QTest::addColumn<QStyleHelper::WidgetSizePolicy>("size");
@@ -133,7 +137,7 @@ void tst_QMacStyle::sizeHints()
     QCOMPARE(sh(&comboBox3).height(), SIZE(32, -1, -1));
 
     QSlider slider1(Qt::Horizontal, &w);
-    QCOMPARE(sh(&slider1).height(), SIZE(15, 12, 10));
+    QCOMPARE(sh(&slider1).height(), SIZE(bigSurOrAbove() ? 18 : 15, 12, 10));
 
     slider1.setTickPosition(QSlider::TicksAbove);
     QCOMPARE(sh(&slider1).height(), SIZE(24, 17, 16));  // Builder
@@ -142,7 +146,7 @@ void tst_QMacStyle::sizeHints()
     QCOMPARE(sh(&slider1).height(), SIZE(24, 17, 16));  // Builder
 
     slider1.setTickPosition(QSlider::TicksBothSides);
-    QVERIFY(sh(&slider1).height() > SIZE(15, 12, 10));  // common sense
+    QVERIFY(sh(&slider1).height() > SIZE(bigSurOrAbove() ? 18 : 15, 12, 10));  // common sense
 
     QPushButton ok1("OK", &w);
     QPushButton cancel1("Cancel", &w);