diff --git a/sha1_name.c b/sha1_name.c
index 9356ac246d..66365049a7 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -269,7 +269,7 @@ static int disambiguate_treeish_only(const unsigned char *sha1, void *cb_data_un
 		return 0;
 
 	/* We need to do this the hard way... */
-	obj = deref_tag(lookup_object(sha1), NULL, 0);
+	obj = deref_tag(parse_object(sha1), NULL, 0);
 	if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
 		return 1;
 	return 0;
diff --git a/t/t1512-rev-parse-disambiguation.sh b/t/t1512-rev-parse-disambiguation.sh
index 30e0b80f05..dfd356721e 100755
--- a/t/t1512-rev-parse-disambiguation.sh
+++ b/t/t1512-rev-parse-disambiguation.sh
@@ -264,6 +264,13 @@ test_expect_success 'ambiguous commit-ish' '
 	test_must_fail git log 000000000...
 '
 
+# There are three objects with this prefix: a blob, a tree, and a tag. We know
+# the blob will not pass as a treeish, but the tree and tag should (and thus
+# cause an error).
+test_expect_success 'ambiguous tags peel to treeish' '
+	test_must_fail git rev-parse 0000000000f^{tree}
+'
+
 test_expect_success 'rev-parse --disambiguate' '
 	# The test creates 16 objects that share the prefix and two
 	# commits created by commit-tree in earlier tests share a