Ionic g page

I am trying to create a new page / component in my ionic 2 application called page2_1 but when I use the command ionic g page page2_1 I get pages and a folder called page-2_1 (with a hyphen added).

I already have a page called page2 so is this why? Or is it that using _'s is a no no? It also happens when I try to create a page called page21 so I think perhaps it is encountering the page2 part of the file name and then adding a hyphen automatically.

Any advice would be much appreciated. I have created the page manually and everything seems to work when it has an underscore.