diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 0fe35d1b5a..4770708063 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -2777,10 +2777,10 @@ static void get_object_list(int ac, const char **av)
 				continue;
 			}
 			if (starts_with(line, "--shallow ")) {
-				unsigned char sha1[20];
-				if (get_sha1_hex(line + 10, sha1))
+				struct object_id oid;
+				if (get_oid_hex(line + 10, &oid))
 					die("not an SHA-1 '%s'", line + 10);
-				register_shallow(sha1);
+				register_shallow(&oid);
 				use_bitmap_index = 0;
 				continue;
 			}
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index f96834f42c..6f0f788b0c 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -858,7 +858,7 @@ static int update_shallow_ref(struct command *cmd, struct shallow_info *si)
 	 * not lose these new roots..
 	 */
 	for (i = 0; i < extra.nr; i++)
-		register_shallow(extra.oid[i].hash);
+		register_shallow(&extra.oid[i]);
 
 	si->shallow_ref[cmd->index] = 0;
 	oid_array_clear(&extra);
diff --git a/commit.c b/commit.c
index 73c78c2b80..ec41ba5e09 100644
--- a/commit.c
+++ b/commit.c
@@ -216,9 +216,9 @@ int for_each_commit_graft(each_commit_graft_fn fn, void *cb_data)
 	return ret;
 }
 
-int unregister_shallow(const unsigned char *sha1)
+int unregister_shallow(const struct object_id *oid)
 {
-	int pos = commit_graft_pos(sha1);
+	int pos = commit_graft_pos(oid->hash);
 	if (pos < 0)
 		return -1;
 	if (pos + 1 < commit_graft_nr)
diff --git a/commit.h b/commit.h
index 7b1986d5c8..884177b8fa 100644
--- a/commit.h
+++ b/commit.h
@@ -263,8 +263,8 @@ extern struct commit_list *get_merge_bases_many_dirty(struct commit *one, int n,
 
 struct oid_array;
 struct ref;
-extern int register_shallow(const unsigned char *sha1);
-extern int unregister_shallow(const unsigned char *sha1);
+extern int register_shallow(const struct object_id *oid);
+extern int unregister_shallow(const struct object_id *oid);
 extern int for_each_commit_graft(each_commit_graft_fn, void *);
 extern int is_repository_shallow(void);
 extern struct commit_list *get_shallow_commits(struct object_array *heads,
diff --git a/fetch-pack.c b/fetch-pack.c
index b42d01f422..d455ef97af 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -417,7 +417,7 @@ static int find_common(struct fetch_pack_args *args,
 			if (skip_prefix(line, "shallow ", &arg)) {
 				if (get_oid_hex(arg, &oid))
 					die(_("invalid shallow line: %s"), line);
-				register_shallow(oid.hash);
+				register_shallow(&oid);
 				continue;
 			}
 			if (skip_prefix(line, "unshallow ", &arg)) {
@@ -428,7 +428,7 @@ static int find_common(struct fetch_pack_args *args,
 				/* make sure that it is parsed as shallow */
 				if (!parse_object(oid.hash))
 					die(_("error in object: %s"), line);
-				if (unregister_shallow(oid.hash))
+				if (unregister_shallow(&oid))
 					die(_("no shallow found: %s"), line);
 				continue;
 			}
diff --git a/shallow.c b/shallow.c
index 25b6db989b..c520ae3aea 100644
--- a/shallow.c
+++ b/shallow.c
@@ -27,13 +27,13 @@ void set_alternate_shallow_file(const char *path, int override)
 	alternate_shallow_file = xstrdup_or_null(path);
 }
 
-int register_shallow(const unsigned char *sha1)
+int register_shallow(const struct object_id *oid)
 {
 	struct commit_graft *graft =
 		xmalloc(sizeof(struct commit_graft));
-	struct commit *commit = lookup_commit(sha1);
+	struct commit *commit = lookup_commit(oid->hash);
 
-	hashcpy(graft->oid.hash, sha1);
+	oidcpy(&graft->oid, oid);
 	graft->nr_parent = -1;
 	if (commit && commit->object.parsed)
 		commit->parents = NULL;
@@ -65,10 +65,10 @@ int is_repository_shallow(void)
 	is_shallow = 1;
 
 	while (fgets(buf, sizeof(buf), fp)) {
-		unsigned char sha1[20];
-		if (get_sha1_hex(buf, sha1))
+		struct object_id oid;
+		if (get_oid_hex(buf, &oid))
 			die("bad shallow line: %s", buf);
-		register_shallow(sha1);
+		register_shallow(&oid);
 	}
 	fclose(fp);
 	return is_shallow;
diff --git a/upload-pack.c b/upload-pack.c
index ffb028d623..20f87cd383 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -642,7 +642,7 @@ static void send_shallow(struct commit_list *result)
 		if (!(object->flags & (CLIENT_SHALLOW|NOT_SHALLOW))) {
 			packet_write_fmt(1, "shallow %s",
 					 oid_to_hex(&object->oid));
-			register_shallow(object->oid.hash);
+			register_shallow(&object->oid);
 			shallow_nr++;
 		}
 		result = result->next;
@@ -667,7 +667,7 @@ static void send_unshallow(const struct object_array *shallows)
 			 * parse and add the parents to the want list, then
 			 * re-register it.
 			 */
-			unregister_shallow(object->oid.hash);
+			unregister_shallow(&object->oid);
 			object->parsed = 0;
 			parse_commit_or_die((struct commit *)object);
 			parents = ((struct commit *)object)->parents;
@@ -679,7 +679,7 @@ static void send_unshallow(const struct object_array *shallows)
 			add_object_array(object, NULL, &extra_edge_obj);
 		}
 		/* make sure commit traversal conforms to client */
-		register_shallow(object->oid.hash);
+		register_shallow(&object->oid);
 	}
 }
 
@@ -883,7 +883,7 @@ static void receive_needs(void)
 		if (shallows.nr > 0) {
 			int i;
 			for (i = 0; i < shallows.nr; i++)
-				register_shallow(shallows.objects[i].item->oid.hash);
+				register_shallow(&shallows.objects[i].item->oid);
 		}
 
 	shallow_nr += shallows.nr;