diff --git a/src/gui.c b/src/gui.c
index 36d6975..34f9f20 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -4500,7 +4500,7 @@
 	for (;;)
 	{
 	    w = chartabsize(p, col);
-	    mb_ptr_adv(p);
+	    MB_PTR_ADV(p);
 	    if (*p == NUL)		/* don't count the last character */
 		break;
 	    col += w;