Thread:Support/Prefix for RandomInCategory

With 71997 a message key 'randomincategory' was added in core. This is in conflict with the same message key in mw:Extension:RandomInCategory now. Therefore I added a prefix to mediawiki-defines.txt. And [//translatewiki.net/w/i.php?title=Special%3ALog&type=move&user=Raymond&page=MediaWiki%3ARandomincategory&pattern=1&year=&month=-1 moved the messages onwiki]. But the next export removed the translations completly from the i18n file. What does I have done wrong?