@a specifier with 'dummy' scoreboard targets players with '@a' as name instead of all players

While using the scoreboard command with the type 'dummy', attempting to add points to '@a' players will report back 'failed to find player named @a'.

I tried recreating the scoreboard, changing its name, and using different values. @p, @r, and other scoreboard types seemed to work, but @a and dummy didn't work. I even invited friends onto my server with the commands in place with no luck.