diff --git a/README.md b/README.md
index e82520c..a5d2dda 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@
 [![Coverage Status](https://coveralls.io/repos/github/Rob--W/proxy-from-env/badge.svg?branch=master)](https://coveralls.io/github/Rob--W/proxy-from-env?branch=master)
 
 `proxy-from-env` is a Node.js package that exports a function (`getProxyForUrl`)
-that takes an input URL (a string or
+that takes an input URL (a string, a `URL` instance, or
 [`url.parse`](https://nodejs.org/docs/latest/api/url.html#url_url_parsing)'s
 return value) and returns the desired proxy URL (also a string) based on
 standard proxy environment variables. If no proxy is set, an empty string is
diff --git a/index.js b/index.js
index df75004..d051de5 100644
--- a/index.js
+++ b/index.js
@@ -17,7 +17,7 @@ var stringEndsWith = String.prototype.endsWith || function(s) {
 };
 
 /**
- * @param {string|object} url - The URL, or the result from url.parse.
+ * @param {string|url.Url|URL} url - The URL, or the result from url.parse.
  * @return {string} The URL of the proxy that should handle the request to the
  *  given URL. If no proxy is set, this will be an empty string.
  */
diff --git a/test.js b/test.js
index abf6542..7f6f95d 100644
--- a/test.js
+++ b/test.js
@@ -92,6 +92,7 @@ describe('getProxyForUrl', function() {
     testProxyUrl(env, '', 'https://example');
     testProxyUrl(env, 'http://http-proxy', 'http://example');
     testProxyUrl(env, 'http://http-proxy', parseUrl('http://example'));
+    testProxyUrl(env, 'http://http-proxy', new URL('http://example'));
 
     // eslint-disable-next-line camelcase
     env.http_proxy = 'http://priority';