Send Approval action to a group of people

Hi. I want to use a SharePoint site group as the source for an Approval action, but when I use the SharePoint site group (which has at least one user) the workflow errors logging that the value is not set. Can someone advise if using a SharePoint site group is a feasible option or should I maybe create an Approvers site list?

 Any worked examples that I can model my WF upon would be great.