Getting 403 when using period in Node Express Routes

I am using a wildcard route to access files in my node app. Some files start with a period. In this case I get 403 Forbidden. Whats the problem with these paths?

Update:

I am using a wildcard route that looks like

app.get('/:area/:place/blob*', function (req, res, next) {

so a route that is causing problems would be one like

/my/area/.git