hasAccessLevel check access rights are wrong in subwikis for anonymous user

Following setup:

• main wiki is view protected via the "Prevent unregistered users from viewing pages"
• sub wiki is public and has local users (i.e. one XWiki.TestUser)
• a page in the subwiki includes a page from the main wiki, i,.e. via

 {{display reference="xwiki:Main.Welcome" type="DOCUMENT"/}}

Expected behaviour: neither XWiki.TestUser nor the anonymous user can view that included document (the include macro should display an error)
Observed behaviour: the logged in user XWiki.TestUser gets an error, but the anonymous user can view the page.

Slightly quicker way to check: as main XWiki.Admin (with PR) paste the following into any page in the subwiki:

{{velocity}}
#set($xxcontext = $xcontext.getContext())
test user: $xwiki.getXWiki().getRightService().hasAccessLevel("view","XWiki.TestUser","xwiki:Main.Welcome",  $xxcontext)
anon view: $xwiki.getXWiki().getRightService().hasAccessLevel("view","XWiki.XWikiGuest", "xwiki:Main.Welcome", $xxcontext)
{{/velocity}}

Output:

test user: false
anon view: true

if the subwiki is closed for anonymous users, too, the effect vanishes.