--- old/src/java.desktop/share/classes/javax/swing/plaf/basic/BasicTabbedPaneUI.java	2018-04-10 15:05:57.397209999 +0530
+++ new/src/java.desktop/share/classes/javax/swing/plaf/basic/BasicTabbedPaneUI.java	2018-04-10 15:05:57.101209999 +0530
@@ -606,6 +606,10 @@
         }
         mnemonicInputMap.put(KeyStroke.getKeyStroke(mnemonic, BasicLookAndFeel.getFocusAcceleratorKeyMask()),
                              "setSelectedIndex");
+        mnemonicInputMap.put(KeyStroke.getKeyStroke(mnemonic,
+                BasicLookAndFeel.getFocusAcceleratorKeyMask() |
+                        InputEvent.ALT_GRAPH_DOWN_MASK),
+                "setSelectedIndex");
         mnemonicToIndexMap.put(Integer.valueOf(mnemonic), Integer.valueOf(index));
     }
 
