Discourse SAML logout issue


I’ve been using discourse-saml plugin to use with discourse Forum site as SP and connect with an IdP that uses simpleSAMLphp. The login works fine, but upon clicking logout, the user session from the IdP is still existing, so when the user logs in again, they are automatically logged in instead of redirecting to the IdP login page. I’ve also just followed the steps in the discourse-saml git, am I missing a setup about the logout?

Any help would be appreciated. Thanks!