Field concatenation or replication?

[trailbound]

The SystemRDL spec appears to support concatenation and replication operators just as Verilog does, but I'm having trouble getting it to work in PeakRDL Regblock. Am I missing some key to making this work? I have a single bit field which I'm trying to use as a mask on a wider bit field.

reg feature_reg {
    field {
        fieldwidth = 1;
    } enable = 1'b1;
};

reg mode_reg {
    field {
        fieldwidth = 3;
    } feature_mode;
};

addrmap csr_hwmask {
    name = "Hardware Mask Test";

    default regwidth = 32;
    default sw = rw;
    default hw = r;

    feature_reg feature;
    mode_reg mode;

    mode.feature_mode->hwmask = {3{feature.enable}};
};

I also tried concatenation...

    mode.feature_mode->hwmask = {feature.enable, feature.enable, feature.enable};

Both lead to the following error.

hwmask.rdl:45:46: fatal: Concatenation operator can only be used for integral or string types
   mode.feature_mode->hwmask = {3{feature.enable}};

I've been trying to determine if there is a way I need to explicitly set the feature.enable field as an integral type, but I thought it would be integral (bit/logic) by default? If anyone has any insight, I'd be grateful!