Index: src/java/org/apache/lucene/index/IndexWriter.java
===================================================================
--- src/java/org/apache/lucene/index/IndexWriter.java	(revision 1097759)
+++ src/java/org/apache/lucene/index/IndexWriter.java	(working copy)
@@ -3008,6 +3008,16 @@
       message("merge seg=" + merge.info.name);
     }
 
+    assert merge.estimatedMergeBytes == 0;
+    for(SegmentInfo info : merge.segments) {
+      if (info.docCount > 0) {
+        final int delCount = numDeletedDocs(info);
+        assert delCount <= info.docCount;
+        final double delRatio = ((double) delCount)/info.docCount;
+        merge.estimatedMergeBytes += info.sizeInBytes(true) * (1.0 - delRatio);
+      }
+    }
+
     // TODO: I think this should no longer be needed (we
     // now build CFS before adding segment to the infos);
     // however, on removing it, tests fail for some reason!
@@ -3133,8 +3143,6 @@
     merge.readers = new ArrayList<SegmentReader>();
     merge.readerClones = new ArrayList<SegmentReader>();
 
-    merge.estimatedMergeBytes = 0;
-
     // This is try/finally to make sure merger's readers are
     // closed:
     boolean success = false;
@@ -3152,13 +3160,6 @@
                                                     -config.getReaderTermsIndexDivisor());
         merge.readers.add(reader);
 
-        final int readerMaxDoc = reader.maxDoc();
-        if (readerMaxDoc > 0) {
-          final int delCount = reader.numDeletedDocs();
-          final double delRatio = ((double) delCount)/readerMaxDoc;
-          merge.estimatedMergeBytes += info.sizeInBytes(true) * (1.0 - delRatio);
-        }
-
         // We clone the segment readers because other
         // deletes may come in while we're merging so we
         // need readers that will not change