Index: lucene/core/src/java/org/apache/lucene/store/DataInput.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/store/DataInput.java	(revision 1301603)
+++ lucene/core/src/java/org/apache/lucene/store/DataInput.java	(working copy)
@@ -106,7 +106,7 @@
     i |= (b & 0x7F) << 21;
     if ((b & 0x80) == 0) return i;
     b = readByte();
-    assert (b & 0x80) == 0;
+    assert (b & 0xf0) == 0;
     return i | ((b & 0x7F) << 28);
   }
 
Index: lucene/core/src/java/org/apache/lucene/store/DataOutput.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/store/DataOutput.java	(revision 1301603)
+++ lucene/core/src/java/org/apache/lucene/store/DataOutput.java	(working copy)
@@ -96,6 +96,7 @@
    * @see DataInput#readVLong()
    */
   public final void writeVLong(long i) throws IOException {
+    assert i >= 0;
     while ((i & ~0x7F) != 0) {
       writeByte((byte)((i & 0x7f) | 0x80));
       i >>>= 7;