Scoreboard Objectives with Underscores do not work in command block player select

Scoreboard objectives with underscores in the name do not properly parse in command block player selection clauses.

We're using a scoreboard objective to determine if a user should be near a command block. (anti-griefing). When we name the objective "trusted_user", it does not work in the command block player selection clause. e.g. @p[score_trusted_user=1]

If we change the name to "trusted", it works.