timeout attribute not supported for input step?

[e-gineer]

I'm trying to use a timeout in an input step:

  step "input" "approve" {

    notifier = notifier[param.approver]

    type = "button"

    subject = param.subject

    prompt = param.prompt

    timeout = param.timeout == -1 ? null : param.timeout

    option "approve" {
      label = "Approve"
      style = "ok"
    }

    option "deny" {
      label = "Deny"
      style = "alert"
    }

  }

I'm getting this error:

2024-03-15 13:42:17 [flowpipe] error Failed watching workspace for mod mod.approval: failed to reload workspace: Internal Error: Failed to decode mod: Unsupported argument: An argument named "timeout" is not expected here.
(/Users/nathan/src/flowpipe-mod-approval/mod.fp:211,5-12)

But the docs say that timeout should work for all step types?