CRM 2016 Web API - Error while retrieving related entities data.

Hi Techies

I'm trying to retrieve all accounts and their primary contact name using the below query.

http://SERVER/ORG/api/data/v8.0/accounts?$select=name&$expand=contact_customer_accounts($select=emailaddress1,lastname,firstname).

The error i'm getting with this is "The navigation properties are not supported with $select clause","type":"Microsoft.Crm.CrmHttpException","stacktrace":" at Microsoft.Crm.Extensibility.OData.CrmODataUtilities.ThrowIfSelectClauseHasNavigationProperty(SelectExpandClause selectExpandClause, Bool".

Is this expected ?

FYI. The same query for a specific account is working fine (shown below)

http://SERVER/ORG/api/data/v8.0/accounts%2825DD0B31-ED8B-E511-80D2-00155D2A68D4%29?$select=name&$expand=contact_customer_accounts($select=emailaddress1,lastname,firstname)

 Is this kind of a limitation with Web API, which wasn't documented ?