diff --git a/projectapi/test/unit/src/org/netbeans/spi/project/support/DelegatingLookupImplTest.java b/projectapi/test/unit/src/org/netbeans/spi/project/support/DelegatingLookupImplTest.java
--- a/projectapi/test/unit/src/org/netbeans/spi/project/support/DelegatingLookupImplTest.java
+++ b/projectapi/test/unit/src/org/netbeans/spi/project/support/DelegatingLookupImplTest.java
@@ -38,6 +38,8 @@
 
 package org.netbeans.spi.project.support;
 
+import java.util.Collection;
+import java.util.concurrent.atomic.AtomicInteger;
 import javax.swing.JButton;
 import javax.swing.JCheckBox;
 import javax.swing.JComboBox;
@@ -138,4 +140,36 @@
         }
     }
 
+    public void testNestedComposites() throws Exception { // #200711
+        final AtomicInteger count = new AtomicInteger();
+        final Runnable orig = new Runnable() {
+            @Override public void run() {
+                count.incrementAndGet();
+            }
+        };
+        class RunnableMerger implements LookupMerger<Runnable> {
+            @Override public Class<Runnable> getMergeableClass() {return Runnable.class;}
+            @Override public Runnable merge(final Lookup lookup) {
+                return new Runnable() {
+                    @Override public void run() {
+                        orig.run();
+                        for (Runnable r : lookup.lookupAll(Runnable.class)) {
+                            assertFalse(r == orig);
+                            assertFalse(r == this);
+                            r.run();
+                        }
+                    }
+                };
+            }
+        }
+        Lookup base = Lookups.fixed(new RunnableMerger());
+        Lookup nested1 = new DelegatingLookupImpl(base, Lookup.EMPTY, null);
+        assertEquals(1, nested1.lookupAll(Runnable.class).size());
+        Lookup nested2 = new DelegatingLookupImpl(nested1, Lookup.EMPTY, null);
+        Collection<? extends Runnable> rs = nested2.lookupAll(Runnable.class);
+        assertEquals(1, rs.size());
+        rs.iterator().next().run();
+        assertEquals(1, count.get());
+    }
+
 }
diff --git a/projectuiapi/src/org/netbeans/spi/project/ui/support/UILookupMergerSupport.java b/projectuiapi/src/org/netbeans/spi/project/ui/support/UILookupMergerSupport.java
--- a/projectuiapi/src/org/netbeans/spi/project/ui/support/UILookupMergerSupport.java
+++ b/projectuiapi/src/org/netbeans/spi/project/ui/support/UILookupMergerSupport.java
@@ -196,7 +196,7 @@
                 ProjectOpenedTrampoline.DEFAULT.projectOpened(defaultInstance);
             }
             for (ProjectOpenedHook poh : lkp.lookupAll(ProjectOpenedHook.class)) {
-                if (poh != defaultInstance && /* XXX #200500: should be: poh != this */!(poh instanceof OpenHookImpl)) {
+                if (poh != defaultInstance && poh != this) {
                     ProjectOpenedTrampoline.DEFAULT.projectOpened(poh);
                 }
             }
@@ -207,7 +207,7 @@
                 ProjectOpenedTrampoline.DEFAULT.projectClosed(defaultInstance);
             }
             for (ProjectOpenedHook poh : lkp.lookupAll(ProjectOpenedHook.class)) {
-                if (poh != defaultInstance && !(poh instanceof OpenHookImpl)) {
+                if (poh != defaultInstance && poh != this) {
                     ProjectOpenedTrampoline.DEFAULT.projectClosed(poh);
                 }
             }