Index: oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/Compactor.java
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/Compactor.java	(revision 1607558)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/segment/Compactor.java	(working copy)
@@ -80,6 +80,12 @@
     }
 
     public SegmentNodeState compact(NodeState before, NodeState after) {
+        if (before instanceof SegmentNodeState
+                && after instanceof SegmentNodeState) {
+            if (before.equals(after)) {
+                return (SegmentNodeState) after;
+            }
+        }
         after.compareAgainstBaseState(before, new CompactDiff(builder));
         return builder.getNodeState();
     }
Index: oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/segment/CompactorTest.java
===================================================================
--- oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/segment/CompactorTest.java	(revision 0)
+++ oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/segment/CompactorTest.java	(revision 0)
@@ -0,0 +1,92 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.jackrabbit.oak.plugins.segment;
+
+import static org.apache.commons.io.FileUtils.deleteQuietly;
+
+import java.io.File;
+
+import junit.framework.Assert;
+
+import org.apache.jackrabbit.oak.Oak;
+import org.apache.jackrabbit.oak.api.CommitFailedException;
+import org.apache.jackrabbit.oak.plugins.segment.memory.MemoryStore;
+import org.apache.jackrabbit.oak.spi.commit.CommitInfo;
+import org.apache.jackrabbit.oak.spi.commit.EmptyHook;
+import org.apache.jackrabbit.oak.spi.security.OpenSecurityProvider;
+import org.apache.jackrabbit.oak.spi.state.NodeBuilder;
+import org.apache.jackrabbit.oak.spi.state.NodeState;
+import org.apache.jackrabbit.oak.spi.state.NodeStore;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class CompactorTest {
+
+    private File src;
+
+    @Before
+    public void before() {
+        long run = System.currentTimeMillis();
+        File root = new File("target");
+        src = new File(root, "tar-compactor-" + run);
+    }
+
+    @After
+    public void after() {
+        deleteQuietly(src);
+    }
+
+    @Test
+    public void testCompactor() throws Exception {
+        MemoryStore source = new MemoryStore();
+        try {
+            NodeStore store = new SegmentNodeStore(source);
+            init(store);
+
+            Compactor compactor = new Compactor(source.getTracker().getWriter());
+            addTestContent(store, 0);
+
+            NodeState initial = store.getRoot();
+            SegmentNodeState after = compactor
+                    .compact(initial, store.getRoot());
+            Assert.assertEquals(store.getRoot(), after);
+
+            addTestContent(store, 1);
+            after = compactor.compact(initial, store.getRoot());
+            Assert.assertEquals(store.getRoot(), after);
+
+        } finally {
+            source.close();
+        }
+
+    }
+
+    private static void init(NodeStore store) {
+        new Oak(store).with(new OpenSecurityProvider())
+                .createContentRepository();
+    }
+
+    private static void addTestContent(NodeStore store, int index)
+            throws CommitFailedException {
+        NodeBuilder builder = store.getRoot().builder();
+        builder.child("test" + index);
+        builder.child("child" + index);
+        store.merge(builder, EmptyHook.INSTANCE, CommitInfo.EMPTY);
+    }
+
+}