diff --git a/src/os_unix.c b/src/os_unix.c
index 7806370..d5c5d84 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -4806,7 +4806,7 @@
 			     * round. */
 			    for (p = buffer; p < buffer + len; p += l)
 			    {
-				l = mb_cptr2len(p);
+				l = MB_CPTR2LEN(p);
 				if (l == 0)
 				    l = 1;  /* NUL byte? */
 				else if (MB_BYTE2LEN(*p) != l)