if (crawl_state.arena)
    {
        switch(channel)
        {
        case MSGCH_PROMPT:
        case MSGCH_GOD:
        case MSGCH_PRAY:
        case MSGCH_DURATION:
        case MSGCH_FOOD:
        case MSGCH_RECOVERY:
        case MSGCH_INTRINSIC_GAIN:
        case MSGCH_MUTATION:
        case MSGCH_ROTTEN_MEAT:
        case MSGCH_EQUIPMENT:
        case MSGCH_FLOOR_ITEMS:
        case MSGCH_MULTITURN_ACTION:
        case MSGCH_EXAMINE:
        case MSGCH_EXAMINE_FILTER:
        case MSGCH_TUTORIAL:
            DEBUGSTR("Invalid channel '%s' in arena mode",
                     channel_to_str(channel).c_str());
            break;
        default:
            break;
        }
    }