diff --git a/CHANGES.txt b/CHANGES.txt
index 1bcf39e53fe..be88c25765f 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -281,6 +281,15 @@ Bug fixes
     fixing the original FieldCache performance problem.
     (Chris Hostetter, Yonik Seeley)
 
+29. LUCENE-140: Fix IndexReader.deleteDocument(int docNum) to
+    correctly raise ArrayIndexOutOfBoundsException when docNum is too
+    large.  Previously, if docNum was only slightly too large (within
+    the same multiple of 8, ie, up to 7 ints beyond maxDoc), no
+    exception would be raised and instead the index would become
+    silently corrupted.  The corruption then only appears much later,
+    in mergeSegments, when the corrupted segment is merged with
+    segment(s) after it. (Mike McCandless)
+
 Optimizations
 
   1. LUCENE-586: TermDocs.skipTo() is now more efficient for
diff --git a/src/java/org/apache/lucene/index/IndexReader.java b/src/java/org/apache/lucene/index/IndexReader.java
index 200306a5e42..9be6dc915a1 100644
--- a/src/java/org/apache/lucene/index/IndexReader.java
+++ b/src/java/org/apache/lucene/index/IndexReader.java
@@ -541,8 +541,8 @@ public abstract class IndexReader {
   public final synchronized void deleteDocument(int docNum) throws IOException {
     if(directoryOwner)
       aquireWriteLock();
-    doDelete(docNum);
     hasChanges = true;
+    doDelete(docNum);
   }
 
 
diff --git a/src/java/org/apache/lucene/index/SegmentMerger.java b/src/java/org/apache/lucene/index/SegmentMerger.java
index 48ec8eb58c0..f55cd55f59c 100644
--- a/src/java/org/apache/lucene/index/SegmentMerger.java
+++ b/src/java/org/apache/lucene/index/SegmentMerger.java
@@ -348,9 +348,9 @@ final class SegmentMerger {
           doc = docMap[doc];                      // map around deletions
         doc += base;                              // convert to merged space
 
-        if (doc < lastDoc)
+        if (lastDoc != 0 && doc <= lastDoc)
           throw new IllegalStateException("docs out of order (" + doc +
-              " < " + lastDoc + " )");
+              " <= " + lastDoc + " )");
 
         df++;
 
diff --git a/src/java/org/apache/lucene/util/BitVector.java b/src/java/org/apache/lucene/util/BitVector.java
index f0c38604ab5..d7797c8d53b 100644
--- a/src/java/org/apache/lucene/util/BitVector.java
+++ b/src/java/org/apache/lucene/util/BitVector.java
@@ -49,12 +49,18 @@ public final class BitVector {
 
   /** Sets the value of <code>bit</code> to one. */
   public final void set(int bit) {
+    if (bit >= size) {
+      throw new ArrayIndexOutOfBoundsException(bit);
+    }
     bits[bit >> 3] |= 1 << (bit & 7);
     count = -1;
   }
 
   /** Sets the value of <code>bit</code> to zero. */
   public final void clear(int bit) {
+    if (bit >= size) {
+      throw new ArrayIndexOutOfBoundsException(bit);
+    }
     bits[bit >> 3] &= ~(1 << (bit & 7));
     count = -1;
   }
@@ -62,6 +68,9 @@ public final class BitVector {
   /** Returns <code>true</code> if <code>bit</code> is one and
     <code>false</code> if it is zero. */
   public final boolean get(int bit) {
+    if (bit >= size) {
+      throw new ArrayIndexOutOfBoundsException(bit);
+    }
     return (bits[bit >> 3] & (1 << (bit & 7))) != 0;
   }
 
@@ -147,7 +156,7 @@ public final class BitVector {
     }
   }
 
-  /** Indicates if the bit vector is sparse and should be saved as a d-gaps list, or desnse, and should be saved as a bit set. */
+  /** Indicates if the bit vector is sparse and should be saved as a d-gaps list, or dense, and should be saved as a bit set. */
   private boolean isSparse() {
     // note: order of comparisons below set to favor smaller values (no binary range search.)
     // note: adding 4 because we start with ((int) -1) to indicate d-gaps format.
diff --git a/src/test/org/apache/lucene/index/TestIndexReader.java b/src/test/org/apache/lucene/index/TestIndexReader.java
index 69a078c62b8..f345cd98a1b 100644
--- a/src/test/org/apache/lucene/index/TestIndexReader.java
+++ b/src/test/org/apache/lucene/index/TestIndexReader.java
@@ -749,6 +749,45 @@ public class TestIndexReader extends TestCase
         diskFree += 10;
       }
     }
+
+    public void testDocsOutOfOrderJIRA140() throws IOException {
+      Directory dir = new RAMDirectory();      
+      IndexWriter writer  = new IndexWriter(dir, new WhitespaceAnalyzer(), true);
+      for(int i=0;i<11;i++) {
+        addDoc(writer, "aaa");
+      }
+      writer.close();
+      IndexReader reader = IndexReader.open(dir);
+
+      // Try to delete an invalid docId, yet, within range
+      // of the final bits of the BitVector:
+
+      boolean gotException = false;
+      try {
+        reader.deleteDocument(11);
+      } catch (ArrayIndexOutOfBoundsException e) {
+        gotException = true;
+      }
+      reader.close();
+
+      writer = new IndexWriter(dir, new WhitespaceAnalyzer(), false);
+
+      // We must add more docs to get a new segment written
+      for(int i=0;i<11;i++) {
+        addDoc(writer, "aaa");
+      }
+
+      try {
+        writer.optimize();
+      } catch (IllegalStateException e) {
+        e.printStackTrace();
+        fail("hit unexpected illegal state exception during optimize");
+      }
+
+      if (!gotException) {
+        fail("delete of out-of-bounds doc number failed to hit exception");
+      }
+    }
     
     private String arrayToString(String[] l) {
       String s = "";