diff --git a/lib/captcha.js b/lib/captcha.js
index 197496f..4d6a71c 100644
--- a/lib/captcha.js
+++ b/lib/captcha.js
@@ -35,11 +35,10 @@ const solve = async (response) => {
           body.push('h-captcha-response=' + captchaResponse);
         }
 
-        const baseUrl = response.url.substring(0, response.url.lastIndexOf('/'));
         const { method, action, enctype } = document.getElementById('challenge-form');
         return {
           method,
-          url: action.startsWith('/') ? baseUrl + action : action,
+          url: new URL(action, response.url),
           headers: {
             'content-type': enctype, // application/x-www-form-urlencoded
           },