diff --git a/commit.c b/commit.c
index bab8d5ab07c..fa26729ba51 100644
--- a/commit.c
+++ b/commit.c
@@ -111,9 +111,9 @@ static const unsigned char *commit_graft_sha1_access(size_t index, void *table)
 	return commit_graft_table[index]->oid.hash;
 }
 
-int commit_graft_pos(struct repository *r, const unsigned char *sha1)
+int commit_graft_pos(struct repository *r, const struct object_id *oid)
 {
-	return hash_pos(sha1, r->parsed_objects->grafts,
+	return hash_pos(oid->hash, r->parsed_objects->grafts,
 			r->parsed_objects->grafts_nr,
 			commit_graft_sha1_access);
 }
@@ -121,7 +121,7 @@ int commit_graft_pos(struct repository *r, const unsigned char *sha1)
 int register_commit_graft(struct repository *r, struct commit_graft *graft,
 			  int ignore_dups)
 {
-	int pos = commit_graft_pos(r, graft->oid.hash);
+	int pos = commit_graft_pos(r, &graft->oid);
 
 	if (0 <= pos) {
 		if (ignore_dups)
@@ -232,7 +232,7 @@ struct commit_graft *lookup_commit_graft(struct repository *r, const struct obje
 {
 	int pos;
 	prepare_commit_graft(r);
-	pos = commit_graft_pos(r, oid->hash);
+	pos = commit_graft_pos(r, oid);
 	if (pos < 0)
 		return NULL;
 	return r->parsed_objects->grafts[pos];
diff --git a/commit.h b/commit.h
index f4e7b0158e2..ecacf9ade36 100644
--- a/commit.h
+++ b/commit.h
@@ -239,7 +239,7 @@ typedef int (*each_commit_graft_fn)(const struct commit_graft *, void *);
 
 struct commit_graft *read_graft_line(struct strbuf *line);
 /* commit_graft_pos returns an index into r->parsed_objects->grafts. */
-int commit_graft_pos(struct repository *r, const unsigned char *sha1);
+int commit_graft_pos(struct repository *r, const struct object_id *oid);
 int register_commit_graft(struct repository *r, struct commit_graft *, int);
 void prepare_commit_graft(struct repository *r);
 struct commit_graft *lookup_commit_graft(struct repository *r, const struct object_id *oid);
diff --git a/shallow.c b/shallow.c
index 91b9e1073c9..9ed18eb8849 100644
--- a/shallow.c
+++ b/shallow.c
@@ -41,7 +41,7 @@ int register_shallow(struct repository *r, const struct object_id *oid)
 
 int unregister_shallow(const struct object_id *oid)
 {
-	int pos = commit_graft_pos(the_repository, oid->hash);
+	int pos = commit_graft_pos(the_repository, oid);
 	if (pos < 0)
 		return -1;
 	if (pos + 1 < the_repository->parsed_objects->grafts_nr)