--- a/mercurial/bdiff.c	Mon Feb 19 10:08:59 2007 +0100
+++ b/mercurial/bdiff.c	Tue Feb 20 22:20:16 2007 +0100
@@ -251,8 +251,8 @@
 	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++;
 	}