Unable to copy pages unless admin

Discovered on xwiki.org, copying http://www.xwiki.org/xwiki/bin/view/Drafts/ContributingExtensions to http://extensions.xwiki.org/xwiki/bin/view/Documentation/ContributingXWikiXarExtensions
To repeat:

• create page on main wiki
• on subwiki, ensure permission to create pages by editing and saving a nonexistant page
• return to page main wiki, click copy on page
• enter taerget: subwiki w/ nonexistant page in same space which was tested
• observe error

Error: You don't have the right to create the target document.