diff --git a/parse-options-cb.c b/parse-options-cb.c
index 7419780a9b..35a941fddc 100644
--- a/parse-options-cb.c
+++ b/parse-options-cb.c
@@ -80,14 +80,14 @@ int parse_opt_verbosity_cb(const struct option *opt, const char *arg,
 
 int parse_opt_commits(const struct option *opt, const char *arg, int unset)
 {
-	unsigned char sha1[20];
+	struct object_id oid;
 	struct commit *commit;
 
 	if (!arg)
 		return -1;
-	if (get_sha1(arg, sha1))
+	if (get_oid(arg, &oid))
 		return error("malformed object name %s", arg);
-	commit = lookup_commit_reference(sha1);
+	commit = lookup_commit_reference(oid.hash);
 	if (!commit)
 		return error("no such commit %s", arg);
 	commit_list_insert(commit, opt->value);