Breaking permissions with SharePoint 2013 & CSOM

Lately I've been doing a lot of work with the Client Side Object Model for SharePoint 2013.  While I have been able to do most things we used to, in the dark days of server side development. However one thing didn't seem to work right, Web.BreakRoleInheritance(bool, bool).
Along the lines of:

web.BreakRoleInheritance(true, true);
clientContext.ExecuteQuery();

Passing the first parameter states the call should break permissions at the web level and copy existing RoleAssignments.  However, I could not get this to work.  Every time the assignments where gone.  Regardless of the values I passed.

The fallback option was to devolve, create a feature with server side code, which looks pretty much identical.  I then call the feature activation automatically through my CSOM service.

public override void FeatureActivated(SPFeatureReceiverProperties properties)
        {
            try
            {
                var web = (SPWeb) properties.Feature.Parent;
                SPSecurity.RunWithElevatedPrivileges(() =>
                {
                    using (var site = new SPSite(web.Site.ID))
                    {
                        using (SPWeb elevatedWeb = site.OpenWeb(web.ID))
                        {
                            elevatedWeb.BreakRoleInheritance(true, true);
                        }
                    }
                   
                });
            }
            catch (Exception ex)
            {
                LogService.LogException(LogCategory.FeatureReceiver, ex);
                throw;
            }
        }

And that worked as expected, role assignments had been copied through from the parent.