diff --git a/jdk/src/solaris/classes/sun/awt/X11/XWindowPeer.java b/jdk/src/solaris/classes/sun/awt/X11/XWindowPeer.java
index 41807dbf047..d3fb2107281 100644
--- a/jdk/src/solaris/classes/sun/awt/X11/XWindowPeer.java
+++ b/jdk/src/solaris/classes/sun/awt/X11/XWindowPeer.java
@@ -146,6 +146,13 @@ class XWindowPeer extends XPanelPeer implements WindowPeer,
 
         params.put(OVERRIDE_REDIRECT, Boolean.valueOf(isOverrideRedirect()));
 
+        SunToolkit.awtLock();
+        try {
+            windows.add(this);
+        } finally {
+            SunToolkit.awtUnlock();
+        }
+
         cachedFocusableWindow = isFocusableWindow();
 
         Font f = target.getFont();