diff --git a/auth.php b/auth.php
index 09fcca0..6a24974 100644
--- a/auth.php
+++ b/auth.php
@@ -83,12 +83,12 @@ class auth_plugin_userkey extends auth_plugin_base {
     /**
      * Login user using userkey and return URL to redirect after.
      *
-     * @return mixed|string URL to redirect.
+     * @return string URL to redirect.
      *
      * @throws \moodle_exception If something went wrong.
      */
     public function user_login_userkey() {
-        global $DB, $SESSION;
+        global $DB, $SESSION, $CFG;
 
         $keyvalue = required_param('key', PARAM_ALPHANUM);
         $wantsurl = optional_param('wantsurl', '', PARAM_URL);
@@ -133,7 +133,7 @@ class auth_plugin_userkey extends auth_plugin_base {
         if (!empty($wantsurl)) {
             return $wantsurl;
         } else {
-            return '/';
+            return $CFG->wwwroot;
         }
     }
 
diff --git a/tests/auth_plugin_test.php b/tests/auth_plugin_test.php
index 6335066..e71b42e 100644
--- a/tests/auth_plugin_test.php
+++ b/tests/auth_plugin_test.php
@@ -635,7 +635,7 @@ class auth_plugin_userkey_testcase extends advanced_testcase {
      * Test that a user loggs in correctly.
      */
     public function test_that_user_logged_in() {
-        global $DB, $USER, $SESSION;
+        global $DB, $USER, $SESSION, $CFG;
 
         $key = new stdClass();
         $key->value = 'UserLogin';
@@ -651,8 +651,7 @@ class auth_plugin_userkey_testcase extends advanced_testcase {
 
         // Using @ is the only way to test this. Thanks moodle!
         $redirect = @$this->auth->user_login_userkey();
-
-        $this->assertEquals('/', $redirect);
+        $this->assertEquals($CFG->wwwroot, $redirect);
         $this->assertEquals($this->user->id, $USER->id);
         $this->assertSame(sesskey(), $USER->sesskey);
         $this->assertObjectHasAttribute('userkey', $SESSION);