diff --git a/src/java.desktop/share/classes/javax/swing/plaf/basic/BasicSeparatorUI.java b/src/java.desktop/share/classes/javax/swing/plaf/basic/BasicSeparatorUI.java
index 0580765e1c0..eea9e9589a6 100644
--- a/src/java.desktop/share/classes/javax/swing/plaf/basic/BasicSeparatorUI.java
+++ b/src/java.desktop/share/classes/javax/swing/plaf/basic/BasicSeparatorUI.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2023, 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
@@ -25,12 +25,12 @@
 
 package javax.swing.plaf.basic;
 
-import javax.swing.*;
 import java.awt.Color;
 import java.awt.Dimension;
 import java.awt.Graphics;
-import java.awt.Insets;
-import java.awt.Rectangle;
+import javax.swing.JComponent;
+import javax.swing.JSeparator;
+import javax.swing.LookAndFeel;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.SeparatorUI;
 
@@ -152,5 +152,13 @@ public class BasicSeparatorUI extends SeparatorUI
     }
 
     public Dimension getMinimumSize( JComponent c ) { return null; }
-    public Dimension getMaximumSize( JComponent c ) { return null; }
+
+    public Dimension getMaximumSize( JComponent c ) {
+        Dimension d = getPreferredSize(c);
+        if (((JSeparator)c).getOrientation() == JSeparator.VERTICAL) {
+            return new Dimension(d.width, Short.MAX_VALUE);
+        } else {
+            return new Dimension(Short.MAX_VALUE, d.height);
+        }
+    }
 }
diff --git a/test/jdk/javax/swing/JToolBar/ToolBarSeparatorSizeTest.java b/test/jdk/javax/swing/JToolBar/ToolBarSeparatorSizeTest.java
new file mode 100644
index 00000000000..47ad7e01b30
--- /dev/null
+++ b/test/jdk/javax/swing/JToolBar/ToolBarSeparatorSizeTest.java
@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2023, 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 4346610
+ * @key headful
+ * @summary Verifies if Adding JSeparator to JToolBar "pushes" buttons added
+ *          after separator to edge
+ * @run main ToolBarSeparatorSizeTest
+ */
+import java.awt.BorderLayout;
+import java.awt.image.BufferedImage;
+import java.awt.Rectangle;
+import java.awt.Robot;
+
+import javax.swing.JButton;
+import javax.swing.JFrame;
+import javax.swing.JPanel;
+import javax.swing.JSeparator;
+import javax.swing.JToolBar;
+import javax.swing.SwingConstants;
+import javax.swing.SwingUtilities;
+
+import javax.imageio.ImageIO;
+
+public class ToolBarSeparatorSizeTest {
+
+    private static JFrame frame;
+    private static JSeparator separator;
+    private static JToolBar toolBar;
+    private static volatile Rectangle toolBarBounds;
+    private static volatile int sepWidth;
+    private static volatile int sepPrefWidth;
+
+    public static void main(String[] args) throws Exception {
+        Robot robot = new Robot();
+        robot.setAutoDelay(100);
+        try {
+            SwingUtilities.invokeAndWait(() -> {
+                frame = new JFrame("ToolBar Separator Test");
+                toolBar = new JToolBar();
+                toolBar.add(new JButton("button 1"));
+                toolBar.add(new JButton("button 2"));
+                separator = new JSeparator(SwingConstants.VERTICAL);
+                toolBar.add(separator);
+                toolBar.add(new JButton("button 3"));
+                frame.getContentPane().setLayout(new BorderLayout());
+                frame.getContentPane().add(toolBar, BorderLayout.NORTH);
+                frame.getContentPane().add(new JPanel(), BorderLayout.CENTER);
+                frame.setSize(400, 100);
+                frame.setLocationRelativeTo(null);
+                frame.setVisible(true);
+            });
+            robot.waitForIdle();
+            robot.delay(1000);
+            SwingUtilities.invokeAndWait(() -> {
+                toolBarBounds = new Rectangle(toolBar.getLocationOnScreen(),
+                                              toolBar.getSize());
+                sepWidth = separator.getSize().width;
+                sepPrefWidth = separator.getPreferredSize().width;
+            });
+            if (sepWidth != sepPrefWidth) {
+                System.out.println("size " + sepWidth);
+                System.out.println("preferredSize " + sepPrefWidth);
+                BufferedImage img = robot.createScreenCapture(toolBarBounds);
+                ImageIO.write(img, "png", new java.io.File("image.png"));
+                throw new RuntimeException("Separator size is too wide");
+            }
+        } finally {
+            SwingUtilities.invokeAndWait(() -> {
+                if (frame != null) {
+                    frame.dispose();
+                }
+            });
+        }
+    }
+}