deno.jsonc "unstable" format?

"unstable": [
  "broadcast-channel",
  "ffi",
  "fs",
  "kv",
  "net",
  "http",
  "worker-options",
  "cron"
],

error: ReferenceError: BroadcastChannel is not defined

"unstable": {
  "type": "array",
  "description": "List of unstable features to enable.",
  "items": {
    "type": "string"
  }
}