OAuth with multiple scopes not working in Zendesk SELL

I am trying to integrate my application with Zendesk sell and in order to create the access token with Oauth code flow, I am trying to set the scopes. But multiple scopes are not working. 

For example: a scope with read and write doesnt work

https://{subdomain}.zendesk.com/oauth/authorizations/new?response_type=code&redirect_uri={your_redirect_url}&client_id={your_unique_identifier}&scope=read%20write

If I set only to read or write, it will work



https://{subdomain}.zendesk.com/oauth/authorizations/new?response_type=code&redirect_uri={your_redirect_url}&client_id={your_unique_identifier}&scope=read