jqplot show highlighter on only one chart

I have a jqplot chart with two data lines. Only one should have the highlighter enabled. I tried this:

series:[
    {
        highlighter: {
            formatString: "",
            show: false
        }
    },
    {
        highlighter: {
            formatString: "Day %s: %d",
            show: true
        }
    }
]

But unfortunately, this doesn't work: the highlighter shows a small empty dot at the first line, whereas it should show nothing.

How do I show the highlighter on one chart and not on the other?