Index: src/java/org/apache/lucene/index/SegmentMerger.java
===================================================================
--- src/java/org/apache/lucene/index/SegmentMerger.java	(revision 320607)
+++ src/java/org/apache/lucene/index/SegmentMerger.java	(working copy)
@@ -313,7 +313,7 @@
       SegmentMergeInfo smi = smis[i];
       TermPositions postings = smi.postings;
       int base = smi.base;
-      int[] docMap = smi.docMap;
+      int[] docMap = smi.getDocMap();
       postings.seek(smi.termEnum);
       while (postings.next()) {
         int doc = postings.doc();
Index: src/java/org/apache/lucene/index/SegmentMergeInfo.java
===================================================================
--- src/java/org/apache/lucene/index/SegmentMergeInfo.java	(revision 320607)
+++ src/java/org/apache/lucene/index/SegmentMergeInfo.java	(working copy)
@@ -24,7 +24,7 @@
   TermEnum termEnum;
   IndexReader reader;
   TermPositions postings;
-  int[] docMap = null;				  // maps around deleted docs
+  int[] docMap;  // initialized/returned from getDocMap()
 
   SegmentMergeInfo(int b, TermEnum te, IndexReader r)
     throws IOException {
@@ -33,7 +33,11 @@
     termEnum = te;
     term = te.term();
     postings = reader.termPositions();
+  }
 
+  // maps around deleted docs
+  int[] getDocMap() {
+    if (docMap == null) {
     // build array which maps document numbers around deletions 
     if (reader.hasDeletions()) {
       int maxDoc = reader.maxDoc();
@@ -47,6 +51,8 @@
       }
     }
   }
+    return docMap;
+  }
 
   final boolean next() throws IOException {
     if (termEnum.next()) {