Extension does not properly detect filenames beginning with '$' if they're already in a csproj file

[isochronous]

We occasionally name files with a '$' at the beginning of the name so that they're guaranteed to show up first in any alphanumeric sort. The problem is that the extension doesn't pick up on files like that already in the .csproj file. Any time I open any files with a filename beginning with '$', I get the "file is not in the csproj file, would you like to add it?" message, despite said file definitely already being there. I'm assuming it's a regex issue.