In Mercurial, untracked files are not shelved

To reproduce:

1. Clone a Mercurial repo.
2. Change a file in the project
3. Add a file to the project
4. In the ST "Working Copy" view, tick the checkbox next to the newly added file
5. Click "Shelve" on the toolbar
6. The modification to the existing file is shelved, but the newly added file is not; it remains in the working copy.

I would expect the following behaviour:

• If the newly added file is ticked, it should be shelved
• Otherwise, it should remain in the working copy

The workaround is to either:

• Use some IDE feature to do the shelving (e.g. IDEA allows fine-grained control of what to shelve)
• Use the file system (e.g. Finder or command line) tools to move the file out of the project (not very handy because you have to remember where to put it back afterwards)