diff --git a/src/undo.c b/src/undo.c
index 833deca..039321c 100644
--- a/src/undo.c
+++ b/src/undo.c
@@ -833,7 +833,7 @@
 		    munged_name = vim_strsave(ffname);
 		    if (munged_name == NULL)
 			return NULL;
-		    for (p = munged_name; *p != NUL; mb_ptr_adv(p))
+		    for (p = munged_name; *p != NUL; MB_PTR_ADV(p))
 			if (vim_ispathsep(*p))
 			    *p = '%';
 		}