Linter for Teensy doesn't work

Using Teensy 3.5. The Linter doesn’t work in main.cpp. But the Linter works in the .cpp and .h files of the library folder. IDE 1.7.2, Core 3.2.1, Atom 1.14.1x64, macOS Sierra 10.12.3
Update: The Linter works only in .h files not in .cpp files.