wildcard redirects not working from 'firebase serve'

I'm trying to redirect some requests from `firebase serve` to `pub serve` (Dart's local server) on a local machine, but the wildcard redirects seem to be not working.

I'm using the following `firebase.json`
```
{
"database": {
"rules": "database.rules.json"
},
"hosting": {
"public": "web",
"redirects": [{
// Following works:
// "source" : "/packages/web_components/webcomponents-lite.min.js",
// "destination" : "http://localhost:8080/packages/web_components/webcomponents-lite.min.js",

// Following doesn't work:
"source" : "/packages/:file*",
"destination" : "http://localhost:8080/packages/:file*"
}]
}
}
```

firebase-cli version: 3.7.0
superstatic version: 4.1.0
Windows 10 Pro x64