Internal error

[19f0b5f03bcf1dc7491ca1ad] /wiki/index.php?title=Special:UserLogin&returnto=Category%3ADiablo+III&returntoquery=diff%3D40038%26oldid%3D38000 Error from line 710 of /var/www/wiki/includes/exception/MWExceptionHandler.php: Class "FormatJson" not found

Backtrace:

#0 /var/www/wiki/includes/exception/MWExceptionHandler.php(262): MWExceptionHandler::logError()
#1 /var/www/wiki/includes/AutoLoader.php(109): MWExceptionHandler::handleError()
#2 /var/www/wiki/includes/AutoLoader.php(109): require(string)
#3 /var/www/wiki/includes/xml/Xml.php(667): AutoLoader::autoload()
#4 /var/www/wiki/includes/xml/Xml.php(683): Xml::encodeJsVar()
#5 /var/www/wiki/includes/resourceloader/ResourceLoader.php(1396): Xml::encodeJsCall()
#6 /var/www/wiki/includes/resourceloader/ResourceLoader.php(1246): ResourceLoader::makeLoaderImplementScript()
#7 /var/www/wiki/includes/resourceloader/ResourceLoaderClientHtml.php(444): ResourceLoader->makeModuleResponse()
#8 /var/www/wiki/includes/resourceloader/ResourceLoaderClientHtml.php(357): ResourceLoaderClientHtml::makeLoad()
#9 /var/www/wiki/includes/resourceloader/ResourceLoaderClientHtml.php(292): ResourceLoaderClientHtml->getLoad()
#10 /var/www/wiki/includes/OutputPage.php(3087): ResourceLoaderClientHtml->getHeadHtml()
#11 /var/www/wiki/includes/skins/SkinTemplate.php(405): OutputPage->headElement()
#12 /var/www/wiki/includes/skins/SkinTemplate.php(127): SkinTemplate->prepareQuickTemplate()
#13 /var/www/wiki/includes/skins/SkinTemplate.php(144): SkinTemplate->generateHTML()
#14 /var/www/wiki/includes/OutputPage.php(2624): SkinTemplate->outputPage()
#15 /var/www/wiki/includes/MediaWiki.php(954): OutputPage->output()
#16 /var/www/wiki/includes/MediaWiki.php(967): MediaWiki->{closure}()
#17 /var/www/wiki/includes/MediaWiki.php(547): MediaWiki->main()
#18 /var/www/wiki/index.php(53): MediaWiki->run()
#19 /var/www/wiki/index.php(46): wfIndexMain()
#20 {main}