diff --git a/src/testing.c b/src/testing.c
index 448c01c..48ba14d 100644
--- a/src/testing.c
+++ b/src/testing.c
@@ -101,7 +101,7 @@
     {
 	same_len = 1;
 	s = p;
-	c = mb_ptr2char_adv(&s);
+	c = mb_cptr2char_adv(&s);
 	clen = s - p;
 	while (*s != NUL && c == mb_ptr2char(s))
 	{