diff --git a/Provider.php b/Provider.php
index 90d4b3b..b7e3a2f 100644
--- a/Provider.php
+++ b/Provider.php
@@ -45,11 +45,19 @@ protected function getOktaUrl()
     }
 
     /**
-     * {@inheritdoc}
+     * Returns the Auth Server ID based on config option 'auth_server_id'.
+     *
+     * @return string
      */
     protected function getAuthServerId()
     {
-        return $this->getConfig('auth_server_id', 'default');
+        $auth_server_id = $this->getConfig('auth_server_id', null);
+
+        if ($auth_server_id) {
+            return $auth_server_id.'/';
+        }
+
+        return '';
     }
 
     /**
@@ -65,7 +73,7 @@ public static function additionalConfigKeys()
      */
     protected function getAuthUrl($state)
     {
-        return $this->buildAuthUrlFromBase($this->getOktaUrl().'/oauth2/'.$this->getAuthServerId().'/v1/authorize', $state);
+        return $this->buildAuthUrlFromBase($this->getOktaUrl().'/oauth2/'.$this->getAuthServerId().'v1/authorize', $state);
     }
 
     /**
@@ -81,7 +89,7 @@ protected function getTokenUrl()
      */
     protected function getUserByToken($token)
     {
-        $response = $this->getHttpClient()->get($this->getOktaUrl().'/oauth2/'.$this->getAuthServerId().'/v1/userinfo', [
+        $response = $this->getHttpClient()->get($this->getOktaUrl().'/oauth2/'.$this->getAuthServerId().'v1/userinfo', [
             'headers' => [
                 'Authorization' => 'Bearer '.$token,
             ],
diff --git a/README.md b/README.md
index ad70078..17f7188 100644
--- a/README.md
+++ b/README.md
@@ -21,7 +21,9 @@ Please see the [Base Installation Guide](https://socialiteproviders.com/usage/),
 
 #### Custom Auth Server
 
-If you're using a custom auth server, pass the `auth_server_id` config option. For more information, see the [okta docs](https://developer.okta.com/docs/concepts/auth-servers/).
+If you're using Okta Developer you should set `auth_server_id` config option appropriately. It should be set to "default", or to the server id of your Custom Authorization Server.
+
+For more information, see the [okta docs](https://developer.okta.com/docs/concepts/auth-servers/).
 
 ### Add provider event listener