# Tweet by [@keefmoon](http://twitter.com/keefmoon) on 2016-09-10 08:57:37 > [!INFO] Archived from [original tweet](http://twitter.com/keefmoon/status/774532268530528256) RT @ayanonagon: Whatever happened to the warnings about modifying system header files in Xcode? Accidentally deleted some and it was baaaaa…