diff --git a/src/plugins/platforms/cocoa/qcocoawindow.mm b/src/plugins/platforms/cocoa/qcocoawindow.mm
index 60152b56b20..651fedb26ea 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.mm
+++ b/src/plugins/platforms/cocoa/qcocoawindow.mm
@@ -1620,6 +1620,7 @@ void QCocoaWindow::applyContentBorderThickness(NSWindow *window)
 
     if (!m_drawContentBorderGradient) {
         [window setStyleMask:[window styleMask] & ~NSTexturedBackgroundWindowMask];
+        [[[window contentView] superview] setNeedsDisplay:YES];
         return;
     }
 
@@ -1650,6 +1651,8 @@ void QCocoaWindow::applyContentBorderThickness(NSWindow *window)
 
     [window setContentBorderThickness:effectiveBottomContentBorderThickness forEdge:NSMinYEdge];
     [window setAutorecalculatesContentBorderThickness:NO forEdge:NSMinYEdge];
+
+    [[[window contentView] superview] setNeedsDisplay:YES];
 }
 
 void QCocoaWindow::updateNSToolbar()
diff --git a/src/widgets/widgets/qmainwindow.cpp b/src/widgets/widgets/qmainwindow.cpp
index 90cfb1d7cb3..358569a5e45 100644
--- a/src/widgets/widgets/qmainwindow.cpp
+++ b/src/widgets/widgets/qmainwindow.cpp
@@ -1519,6 +1519,7 @@ void QMainWindow::setUnifiedTitleAndToolBarOnMac(bool set)
 
         typedef void (*SetContentBorderEnabledFunction)(QWindow *window, bool enable);
         (reinterpret_cast<SetContentBorderEnabledFunction>(function))(window()->windowHandle(), set);
+        update();
     }
 #endif