diff --git a/lib/checkout.js b/lib/checkout.js
index 652f6116a..f99e27fd0 100644
--- a/lib/checkout.js
+++ b/lib/checkout.js
@@ -40,7 +40,7 @@ Checkout.index = function(repo, index, options) {
 *
 * @async
 * @param {Repository} repo
-* @param {Oid|Tree|Commit|Reference} treeish
+* @param {String|Tree|Commit|Reference} treeish
 * @param {CheckoutOptions} [options]
 * @return {Void} checkout complete
 */