Index: /trunk/src/VBox/Frontends/VirtualBox/src/widgets/UITabBar.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/widgets/UITabBar.cpp	(revision 68252)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/widgets/UITabBar.cpp	(revision 68253)
@@ -332,5 +332,9 @@
             m_pButtonClose->setIconSize(QSize(iMetricCloseButton, iMetricCloseButton));
             m_pButtonClose->setIcon(UIIconPool::iconSet(":/close_16px.png"));
+#ifdef VBOX_WS_MAC
             m_pButtonClose->setStyleSheet("QToolButton { border: 0px }");
+#else
+            m_pButtonClose->setAutoRaise(true);
+#endif
             connect(m_pButtonClose, &QToolButton::clicked, this, &UITabBarItem::sltCloseClicked);
         }