--- a/src/java.desktop/share/classes/com/sun/java/swing/plaf/windows/WindowsRootPaneUI.java	Mon Apr 06 18:41:06 2015 +0400
+++ b/src/java.desktop/share/classes/com/sun/java/swing/plaf/windows/WindowsRootPaneUI.java	Mon Apr 06 19:03:09 2015 +0400
@@ -197,6 +197,10 @@
                 root = null;
                 winAncestor = null;
             } else {
+                if (WindowsLookAndFeel.isMnemonicHidden() && ev.isAltDown()) {
+                    WindowsLookAndFeel.setMnemonicHidden(false);
+                    WindowsGraphicsUtils.repaintMnemonicsInWindow(winAncestor);
+                }
                 altKeyPressed = false;
             }
             return false;

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/javax/swing/plaf/windows/6921687/bug6921687.java	Mon Apr 06 19:03:09 2015 +0400
@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/* @test
+   @bug 6921687
+   @summary Mnemonic disappears after repeated attempts to open menu items using
+   mnemonics
+   @author Semyon Sadetsky
+   @library /lib/testlibrary
+   @build jdk.testlibrary.OSInfo
+  */
+
+
+import jdk.testlibrary.OSInfo;
+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.KeyEvent;
+
+
+public class bug6921687 {
+
+    private static Class lafClass;
+    private static JFrame frame;
+
+    public static void main(String[] args) throws Exception {
+        if (OSInfo.getOSType() != OSInfo.OSType.WINDOWS) {
+            System.out.println("Only Windows platform test. Test is skipped.");
+            System.out.println("ok");
+            return;
+        }
+        lafClass = Class.forName(UIManager.getSystemLookAndFeelClassName());
+        UIManager.setLookAndFeel((LookAndFeel) lafClass.newInstance());
+        try {
+            SwingUtilities.invokeAndWait(new Runnable() {
+                public void run() {
+                    frame = new JFrame();
+                    frame.setUndecorated(true);
+                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+                    setup(frame);
+                }
+            });
+
+            final Robot robot = new Robot();
+            robot.setAutoDelay(20);
+            robot.keyPress(KeyEvent.VK_ALT);
+            robot.keyPress(KeyEvent.VK_F);
+            robot.keyRelease(KeyEvent.VK_F);
+            robot.keyRelease(KeyEvent.VK_ALT);
+            robot.waitForIdle();
+            checkMnemonics();
+
+            robot.keyPress(KeyEvent.VK_ALT);
+            robot.keyPress(KeyEvent.VK_S);
+            robot.keyRelease(KeyEvent.VK_S);
+            robot.keyRelease(KeyEvent.VK_ALT);
+            robot.waitForIdle();
+            checkMnemonics();
+            System.out.println("ok");
+        } finally {
+            frame.dispose();
+        }
+
+    }
+
+    private static void checkMnemonics() throws Exception {
+        if ((Boolean) lafClass.getMethod("isMnemonicHidden").invoke(lafClass)) {
+            throw new RuntimeException("Mnemonics are hidden");
+        }
+    }
+
+    private static void setup(JFrame frame) {
+        JMenuBar menuBar = new JMenuBar();
+        frame.setJMenuBar(menuBar);
+
+        // First Menu, F - Mnemonic
+        JMenu firstMenu = new JMenu("First Menu");
+        firstMenu.setMnemonic(KeyEvent.VK_F);
+        firstMenu.add(new JMenuItem("One", KeyEvent.VK_O));
+        firstMenu.add(new JMenuItem("Two", KeyEvent.VK_T));
+        menuBar.add(firstMenu);
+
+        // Second Menu, S - Mnemonic
+        JMenu secondMenu = new JMenu("Second Menu");
+        secondMenu.setMnemonic(KeyEvent.VK_S);
+        secondMenu.add(new JMenuItem("A Menu Item", KeyEvent.VK_A));
+        menuBar.add(secondMenu);
+
+        frame.setSize(350, 250);
+        frame.setVisible(true);
+
+    }
+}
\ No newline at end of file