diff --git a/submodule.c b/submodule.c
index b80ecacf60dc87025336b6b6d6a51acc9321f429..48e3b44e219dffec6f435f0f25f1b74409fa29a9 100644
--- a/submodule.c
+++ b/submodule.c
@@ -965,7 +965,7 @@ static int find_first_merges(struct object_array *result, const char *path,
 			sha1_to_hex(a->object.sha1));
 	init_revisions(&revs, NULL);
 	rev_opts.submodule = path;
-	setup_revisions(sizeof(rev_args)/sizeof(char *)-1, rev_args, &revs, &rev_opts);
+	setup_revisions(ARRAY_SIZE(rev_args)-1, rev_args, &revs, &rev_opts);
 
 	/* save all revisions from the above list that contain b */
 	if (prepare_revision_walk(&revs))