--- a/src/share/classes/javax/swing/plaf/basic/BasicComboBoxUI.java	Mon Jun 03 16:27:44 2013 +0400
+++ b/src/share/classes/javax/swing/plaf/basic/BasicComboBoxUI.java	Mon Jun 03 16:37:13 2013 +0400
@@ -692,9 +692,9 @@
      */
     protected void installComponents() {
         arrowButton = createArrowButton();
-        comboBox.add( arrowButton );
 
         if (arrowButton != null)  {
+            comboBox.add(arrowButton);
             configureArrowButton();
         }
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/javax/swing/JComboBox/6337518/bug6337518.java	Mon Jun 03 16:37:13 2013 +0400
@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2013, 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 6337518
+   @summary Null Arrow Button Throws Exception in BasicComboBoxUI
+   @author Anton Litvinov
+*/
+
+import javax.swing.*;
+import javax.swing.plaf.basic.*;
+
+public class bug6337518 extends BasicComboBoxUI {
+    @Override
+    protected JButton createArrowButton() {
+        return null;
+    }
+
+    public static void main(String[] args) throws Exception {
+        SwingUtilities.invokeAndWait(new Runnable() {
+            @Override
+            public void run() {
+                JComboBox comboBox = new JComboBox();
+                comboBox.setUI(new bug6337518());
+            }
+        });
+    }
+}