Index: src/main/java/org/apache/jackrabbit/oak/plugins/segment/file/TarWriter.java
===================================================================
--- src/main/java/org/apache/jackrabbit/oak/plugins/segment/file/TarWriter.java	(revision 1676729)
+++ src/main/java/org/apache/jackrabbit/oak/plugins/segment/file/TarWriter.java	(working copy)
@@ -31,16 +31,19 @@
 import java.io.IOException;
 import java.io.RandomAccessFile;
 import java.nio.ByteBuffer;
+import java.util.ArrayDeque;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Queue;
 import java.util.Set;
 import java.util.SortedMap;
 import java.util.UUID;
 import java.util.zip.CRC32;
 
 import com.google.common.collect.Lists;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -442,20 +445,28 @@
      * Add all segment ids that are reachable from {@code referencedIds} via
      * this writer's segment graph and subsequently remove those segment ids
      * from {@code referencedIds} that are in this {{TarWriter}} as those can't
-     * be cleaned up anyway.
+     * be cleaned up anyway, because they will not be present in subsequent
+     * readers.
      * @param referencedIds
      * @throws IOException
      */
-    synchronized void collectReferences(Set<UUID> referencedIds) throws IOException {
-        Set<UUID> referenced = newHashSet();
-        for (UUID id : referencedIds) {
-            List<UUID> refs = graph.get(id);
-            if (refs != null) {
-                referenced.addAll(refs);
+    synchronized void collectReferences(Set<UUID> referencedIds)
+            throws IOException {
+
+        Set<UUID> processed = newHashSet();
+        Queue<UUID> ids = new ArrayDeque<UUID>(referencedIds);
+        while (!ids.isEmpty()) {
+            UUID id = ids.poll();
+            if (id != null && processed.add(id)) {
+                if (graph.containsKey(id)) {
+                    Set<UUID> refs = newHashSet(graph.get(id));
+                    refs.removeAll(processed);
+                    referencedIds.addAll(refs);
+                    referencedIds.remove(id);
+                    ids.addAll(refs);
+                }
             }
         }
-        referencedIds.addAll(referenced);
-        referencedIds.removeAll(index.keySet());
     }
 
     //------------------------------------------------------------< Object >--