Adding Site Collection Owners http://ift.tt/1wLKIlv

I'm trying to add an account to the site collection owners on users personal sites. I' using the following but get this error: You need to be a site collection administrator to set this property.

       User spUser = null;
       using (ClientContext clientContext = new ClientContext(siteURL)) {
            clientContext.Credentials = credentials;
            if (clientContext != null)
            {
                spUser = clientContext.Web.EnsureUser(userAccount);
                spUser.IsSiteAdmin = true;
                spUser.Update();

                clientContext.Load(spUser);
                clientContext.ExecuteQuery();
            }
        }

On http://ift.tt/1wLKIlv the user is under site collection Administrators.