diff -r b9dcee25be8e -r 9dc64c8414ca mercurial/bdiff.c
--- a/mercurial/bdiff.c	Sat Mar 03 18:59:54 2007 -0800
+++ b/mercurial/bdiff.c	Sun Mar 04 09:03:21 2007 -0300
@@ -255,8 +255,8 @@
 	if (pos && l.base && t) {
 		/* generate the matching block list */
 		recurse(a, b, pos, 0, an, 0, bn, &l);
-		l.head->a1 = an;
-		l.head->b1 = bn;
+		l.head->a1 = l.head->a2 = an;
+		l.head->b1 = l.head->b2 = bn;
 		l.head++;
 	}