diff --git a/usr.bin/at/at.c b/usr.bin/at/at.c
index fec0df3c133..da930d1d8d1 100644
--- a/usr.bin/at/at.c
+++ b/usr.bin/at/at.c
@@ -356,7 +356,7 @@ writefile(time_t runtimer, char queue)
 	else
 	{
 	    size_t i;
-	    for (i=0; i<sizeof(no_export)/sizeof(no_export[0]); i++)
+	    for (i = 0; i < nitems(no_export); i++)
 	    {
 		export = export
 		    && (strncmp(*atenv, no_export[i],