diff --git a/lucene/src/java/org/apache/lucene/index/BufferedDeletesStream.java b/lucene/src/java/org/apache/lucene/index/BufferedDeletesStream.java
index 47bd8ea5598..88e531fd0eb 100644
--- a/lucene/src/java/org/apache/lucene/index/BufferedDeletesStream.java
+++ b/lucene/src/java/org/apache/lucene/index/BufferedDeletesStream.java
@@ -147,7 +147,7 @@ class BufferedDeletesStream {
   };
   
   /** Resolves the buffered deleted Term/Query/docIDs, into
-   *  actual deleted docIDs in the liveDocs BitVector for
+   *  actual deleted docIDs in the liveDocs MutableBits for
    *  each SegmentReader. */
   public synchronized ApplyDeletesResult applyDeletes(IndexWriter.ReaderPool readerPool, List<SegmentInfo> infos) throws IOException {
     final long t0 = System.currentTimeMillis();
diff --git a/lucene/src/java/org/apache/lucene/index/IndexWriter.java b/lucene/src/java/org/apache/lucene/index/IndexWriter.java
index 36e9a123bd5..c94c47862fe 100644
--- a/lucene/src/java/org/apache/lucene/index/IndexWriter.java
+++ b/lucene/src/java/org/apache/lucene/index/IndexWriter.java
@@ -633,7 +633,7 @@ public class IndexWriter implements Closeable, TwoPhaseCommit {
           }
         }
         assert (info.docCount - liveDocs.count()) == info.getDelCount() + pendingDeleteCount:
-           "delete count mismatch during commit: seg=" + info + " info.delCount=" + info.getDelCount() + " vs BitVector=" + (info.docCount-liveDocs.count() + " pendingDelCount=" + pendingDeleteCount);
+           "delete count mismatch during commit: seg=" + info + " info.delCount=" + info.getDelCount() + " vs MutableBits=" + (info.docCount-liveDocs.count() + " pendingDelCount=" + pendingDeleteCount);
         info.setDelCount(info.getDelCount() + pendingDeleteCount);
         pendingDeleteCount = 0;
         return true;
@@ -2206,7 +2206,7 @@ public class IndexWriter implements Closeable, TwoPhaseCommit {
 
   /**
    * Prepares the {@link SegmentInfo} for the new flushed segment and persists
-   * the deleted documents {@link BitVector}. Use
+   * the deleted documents {@link MutableBits}. Use
    * {@link #publishFlushedSegment(SegmentInfo, FrozenBufferedDeletes)} to
    * publish the returned {@link SegmentInfo} together with its segment private
    * delete packet.