diff -r 1bcfccf16f90 openide.nodes/src/org/openide/nodes/Sheet.java
--- a/openide.nodes/src/org/openide/nodes/Sheet.java	Sun Sep 30 19:13:37 2012 -0700
+++ b/openide.nodes/src/org/openide/nodes/Sheet.java	Sun Oct 28 12:50:26 2012 +0100
@@ -88,7 +88,7 @@
     /** Copy constrcutor.
     * @param ar array to use
     */
-    private Sheet(ArrayList<Set> ar) {
+    Sheet(ArrayList<Set> ar) {
         sets = ar;
     }
 
diff -r 1bcfccf16f90 openide.nodes/test/unit/src/org/openide/nodes/SheetTest.java
--- a/openide.nodes/test/unit/src/org/openide/nodes/SheetTest.java	Sun Sep 30 19:13:37 2012 -0700
+++ b/openide.nodes/test/unit/src/org/openide/nodes/SheetTest.java	Sun Oct 28 12:50:26 2012 +0100
@@ -47,7 +47,11 @@
 import java.beans.PropertyChangeEvent;
 import java.beans.PropertyChangeListener;
 import java.util.*;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicBoolean;
 import org.netbeans.junit.NbTestCase;
+import org.openide.nodes.Node.PropertySet;
+import org.openide.util.Exceptions;
 
 
 
@@ -174,4 +178,47 @@
         
     }
 
+    public void testIncorrectSynchronization() {
+        final CountDownLatch cont = new CountDownLatch(1);
+        final CountDownLatch finish = new CountDownLatch(1);
+        final AtomicBoolean testStarted = new AtomicBoolean();
+        final Sheet test = new Sheet(new ArrayList<Sheet.Set>() {
+            @Override
+            public <T> T[] toArray(T[] a) {
+                if (testStarted.get()) {
+                    cont.countDown();
+                    try {
+                        finish.await();
+                    } catch (InterruptedException ex) {
+                        Exceptions.printStackTrace(ex);
+                    }
+                }
+                return super.toArray(a);
+            }
+        });
+        
+        test.put(new Sheet.Set());
+        
+        final boolean[] wasNull = new boolean[1];
+        
+        new Thread() {
+            @Override public void run() {
+                try {
+                    cont.await();
+                    for (PropertySet set : test.toArray()) {
+                        wasNull[0] |= set == null;
+                    }
+                } catch (InterruptedException ex) {
+                    Exceptions.printStackTrace(ex);
+                }
+                finish.countDown();
+            }
+        }.start();
+
+        testStarted.set(true);
+        
+        test.toArray();
+        
+        assertFalse("No JavaNode in sight, and still returns a null property set?", wasNull[0]);
+    }
 }