Hi, I created a JIRA issue for this problem.. For detailed description please check https://issues.jboss.org/browse/KEYCLOAK-2503 *Basic description:* I want to delete 2 (custom) attributes defined via client representation in body parameter "attributes" via REST admin command "Update the client" (PUT method). 1.) customAttr_1 via not defining in JSON's request body 2.) customAttr_2 via setting with value empty string "" Execution of Update The Client REST request performs successfully with status code 204 No Content. Next I want to check the client representation via GET method. The response returns customAttr_1 and does not return customAttr_2. But If I want to re-create the deleted customAttr_2 (via UPDATE the client), I receive HTTP status code 409 Conflict. Conclusion: 1.) customAttr_1 not deleted 2.) customAttr_2 not present in GET response, but still present in DB in table CLIENT_ATTRIBUTES with value Null. Best Regards, Juraj