PHPStorm - automatically add line comment "//" when hitting return / enter

I don't know what I did to change this, but it used to be that if I started an in-line comment like this:

// My inline comment

and then hit enter/return, PHPStorm would automatically add // (with the space) to the next line, but now when I try it it doesn't happen anymore. I've searched the settings and can't find anything obvious, any ideas?