Currently if you call your sketch 01_Hello.ino and you try to open it with the IDE an error is raised. <img width="511" alt="screenshot 2017-08-07 18 16 10" src="https://user-images.githubusercontent.com/6151328/29070328-2880e900-7c3f-11e7-9ec9-2d3c5cf65d39.png"> Let's allow it please :) https://github.com/arduino/Arduino/blob/472b3b8b399e15316b77c35a75eae67f6d7dfa03/arduino-core/src/processing/app/BaseNoGui.java#L872