Unable to redirect to external URL from doAction method

It's currently not possible to redirect to an external URL (e.g. starting with 'http://') from the doAction:
response.sendRedirect(externalURL);

The following message will be shown: "Can only redirect to an absolute path starting with a '/'"

Probably it has to do with the following in 'org.hippoecm.hst.core.container.ActionValve':

...
if (!requestContext.isPortletContext()) {
responseState.flush();
if(!responseState.getRedirectLocation().startsWith("/"))

{ throw new ContainerException("Can only redirect to an absolute path starting with a '/'"); }

...