Deneb Dashed Line Chart

I am trying to create a dashed line chart but the lines remain solid in the plot area. Legend looks good. Any help would be appreciated. I am using sample stocks data here.

Below is my code

{
"config": {"view": {"continuousWidth": 400, "continuousHeight": 300}},
"data": {"name": "dataset"},
"mark": "line",
"encoding": {
"color": {"field": "symbol", "type": "nominal"},
"strokeDash": {"field": "symbol", "type": "nominal"},
"x": {"field": "date", "type": "temporal"},
"y": {"field": "price", "type": "quantitative"}
}

}

And below is what I am getting

This is what I am looking for