Text in exported chart is hidden when setting style in chart options

[Remolutionary]

I want to report a bug when exporting a chart.
As soon as I start to set fontSize in style options the text is completely missing in the export file.

chart: {
        type: 'area',
        zooming: {
            type: 'x'
        },
        panning: true,
        panKey: 'shift',
        scrollablePlotArea: {
            minWidth: 600
        },
        style: {
        	fontSize: '1.1em'
        }
    },

I created a fiddle to reproduce the issue:
https://jsfiddle.net/yrsv310n/2/

In browser the chart looks like this:

When exporting as png or jpg it looks like this:

Export in svg format works.