diff -r 8c0c75aa3ff4 -r 3633403888ae mercurial/bdiff.c
--- a/mercurial/bdiff.c	Tue Nov 08 18:37:33 2016 +0100
+++ b/mercurial/bdiff.c	Tue Nov 15 21:56:49 2016 +0100
@@ -188,7 +188,7 @@
 					/* same match but closer to half */
 					mi = i;
 					mj = j;
-				} else if (i == mi && mj > bhalf) {
+				} else if (i == mi && (mj > bhalf || i == a1)) {
 					/* same i but best earlier j */
 					mj = j;
 				}