Chart columns overlap X axis

[proteamer]

Hi, I've faced with issue when tried set custom xAxis.lineWidth in Highstock chart.

Actual behaviour

When I set xAxis.lineWidth to 10 I see that chart columns overlap X axis. See image bellow:

Expected behaviour

I tried to set xAxis.lineWidth to 10 in Highcharts chart. It works as expected:

Also I figured out that in Highstock v5.0.4 the same example work as expected.

Live demo with steps to reproduce

Highstock v6.0.7 example: https://jsfiddle.net/unlimit/yjjqL44x/ (works with issue)
Highcharts v6.0.7 example: https://jsfiddle.net/unlimit/ycyy7k5m/ (works as expected)

Product version

Highstock v6.0.7

Affected browser(s)

Google Chrome v65, Safari v11.0.2, etc.

[pawelfus]

Hi @proteamer

Thank your for reporting this issue.

Internal note:
Regression from 0a92202 @KacperMadej

[ppotaczek]

The workaround is to set zIndex for xAxis:

xAxis: { zIndex: 999 }

Live demo: https://jsfiddle.net/BlackLabel/jjk39ass/