DeploymentEnvironment cannot be extended via !ref

[AnnejanBarelds]

It looks like a deploymentEnvironment element cannot be extended by using !ref. The CLI throws an error when I try it:

StructurizrDslParserException: Unexpected tokens (expected: deploymentGroup, deploymentNode, ->)

A minimal repro looks like this:

workspace {
    model {
        de = deploymentEnvironment "DeploymentEnvironment"

        !ref de {
            dn = deploymentNode "DeploymentNode"
        }
    }
}

Obviously the intend is to have the deploymentEnvironment in another file and !include that file.

Should this work, or am I misinterpreting something?