diff --git a/builtin/tag.c b/builtin/tag.c
index 01154ea8dc..b25bf8daa2 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -111,7 +111,7 @@ static int verify_tag(const char *name, const char *ref,
 	if (fmt_pretty)
 		flags = GPG_VERIFY_OMIT_STATUS;
 
-	if (gpg_verify_tag(oid->hash, name, flags))
+	if (gpg_verify_tag(oid, name, flags))
 		return -1;
 
 	if (fmt_pretty)
diff --git a/builtin/verify-tag.c b/builtin/verify-tag.c
index f9a5f7535a..ed8329340f 100644
--- a/builtin/verify-tag.c
+++ b/builtin/verify-tag.c
@@ -56,20 +56,21 @@ int cmd_verify_tag(int argc, const char **argv, const char *prefix)
 	}
 
 	while (i < argc) {
-		unsigned char sha1[20];
+		struct object_id oid;
 		const char *name = argv[i++];
-		if (get_sha1(name, sha1)) {
+
+		if (get_oid(name, &oid)) {
 			had_error = !!error("tag '%s' not found.", name);
 			continue;
 		}
 
-		if (gpg_verify_tag(sha1, name, flags)) {
+		if (gpg_verify_tag(&oid, name, flags)) {
 			had_error = 1;
 			continue;
 		}
 
 		if (fmt_pretty)
-			pretty_print_ref(name, sha1, fmt_pretty);
+			pretty_print_ref(name, oid.hash, fmt_pretty);
 	}
 	return had_error;
 }
diff --git a/commit.c b/commit.c
index cbfd689939..e0888cf0f7 100644
--- a/commit.c
+++ b/commit.c
@@ -199,11 +199,11 @@ static void prepare_commit_graft(void)
 	commit_graft_prepared = 1;
 }
 
-struct commit_graft *lookup_commit_graft(const unsigned char *sha1)
+struct commit_graft *lookup_commit_graft(const struct object_id *oid)
 {
 	int pos;
 	prepare_commit_graft();
-	pos = commit_graft_pos(sha1);
+	pos = commit_graft_pos(oid->hash);
 	if (pos < 0)
 		return NULL;
 	return commit_graft[pos];
@@ -335,7 +335,7 @@ int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long s
 	bufptr += tree_entry_len + 1; /* "tree " + "hex sha1" + "\n" */
 	pptr = &item->parents;
 
-	graft = lookup_commit_graft(item->object.oid.hash);
+	graft = lookup_commit_graft(&item->object.oid);
 	while (bufptr + parent_entry_len < tail && !memcmp(bufptr, "parent ", 7)) {
 		struct commit *new_parent;
 
diff --git a/commit.h b/commit.h
index 4127c298cb..6d857f06c1 100644
--- a/commit.h
+++ b/commit.h
@@ -249,7 +249,7 @@ typedef int (*each_commit_graft_fn)(const struct commit_graft *, void *);
 
 struct commit_graft *read_graft_line(char *buf, int len);
 int register_commit_graft(struct commit_graft *, int);
-struct commit_graft *lookup_commit_graft(const unsigned char *sha1);
+struct commit_graft *lookup_commit_graft(const struct object_id *oid);
 
 extern struct commit_list *get_merge_bases(struct commit *rev1, struct commit *rev2);
 extern struct commit_list *get_merge_bases_many(struct commit *one, int n, struct commit **twos);
diff --git a/fsck.c b/fsck.c
index b4204d772b..2d2d2e9432 100644
--- a/fsck.c
+++ b/fsck.c
@@ -736,7 +736,7 @@ static int fsck_commit_buffer(struct commit *commit, const char *buffer,
 		buffer += 41;
 		parent_line_count++;
 	}
-	graft = lookup_commit_graft(commit->object.oid.hash);
+	graft = lookup_commit_graft(&commit->object.oid);
 	parent_count = commit_list_count(commit->parents);
 	if (graft) {
 		if (graft->nr_parent == -1 && !parent_count)
diff --git a/shallow.c b/shallow.c
index 54359d5490..f5591e56da 100644
--- a/shallow.c
+++ b/shallow.c
@@ -107,7 +107,7 @@ struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
 		cur_depth++;
 		if ((depth != INFINITE_DEPTH && cur_depth >= depth) ||
 		    (is_repository_shallow() && !commit->parents &&
-		     (graft = lookup_commit_graft(commit->object.oid.hash)) != NULL &&
+		     (graft = lookup_commit_graft(&commit->object.oid)) != NULL &&
 		     graft->nr_parent < 0)) {
 			commit_list_insert(commit, &result);
 			commit->object.flags |= shallow_flag;
@@ -398,7 +398,7 @@ void prepare_shallow_info(struct shallow_info *info, struct oid_array *sa)
 	for (i = 0; i < sa->nr; i++) {
 		if (has_object_file(sa->oid + i)) {
 			struct commit_graft *graft;
-			graft = lookup_commit_graft(sa->oid[i].hash);
+			graft = lookup_commit_graft(&sa->oid[i]);
 			if (graft && graft->nr_parent < 0)
 				continue;
 			info->ours[info->nr_ours++] = i;
diff --git a/tag.c b/tag.c
index 47f60ae151..7e10acfb6e 100644
--- a/tag.c
+++ b/tag.c
@@ -33,7 +33,7 @@ static int run_gpg_verify(const char *buf, unsigned long size, unsigned flags)
 	return ret;
 }
 
-int gpg_verify_tag(const unsigned char *sha1, const char *name_to_report,
+int gpg_verify_tag(const struct object_id *oid, const char *name_to_report,
 		unsigned flags)
 {
 	enum object_type type;
@@ -41,20 +41,20 @@ int gpg_verify_tag(const unsigned char *sha1, const char *name_to_report,
 	unsigned long size;
 	int ret;
 
-	type = sha1_object_info(sha1, NULL);
+	type = sha1_object_info(oid->hash, NULL);
 	if (type != OBJ_TAG)
 		return error("%s: cannot verify a non-tag object of type %s.",
 				name_to_report ?
 				name_to_report :
-				find_unique_abbrev(sha1, DEFAULT_ABBREV),
+				find_unique_abbrev(oid->hash, DEFAULT_ABBREV),
 				typename(type));
 
-	buf = read_sha1_file(sha1, &type, &size);
+	buf = read_sha1_file(oid->hash, &type, &size);
 	if (!buf)
 		return error("%s: unable to read file.",
 				name_to_report ?
 				name_to_report :
-				find_unique_abbrev(sha1, DEFAULT_ABBREV));
+				find_unique_abbrev(oid->hash, DEFAULT_ABBREV));
 
 	ret = run_gpg_verify(buf, size, flags);
 
diff --git a/tag.h b/tag.h
index fdfcb4a84a..d469534e82 100644
--- a/tag.h
+++ b/tag.h
@@ -17,7 +17,7 @@ extern int parse_tag_buffer(struct tag *item, const void *data, unsigned long si
 extern int parse_tag(struct tag *item);
 extern struct object *deref_tag(struct object *, const char *, int);
 extern struct object *deref_tag_noverify(struct object *);
-extern int gpg_verify_tag(const unsigned char *sha1,
+extern int gpg_verify_tag(const struct object_id *oid,
 		const char *name_to_report, unsigned flags);
 
 #endif /* TAG_H */