jqPlot - multiline ticks with angle in x-axis

I have a question about ticks in x-axis. I work with jqPlot 0.9.7

My ticks are multiline, like this: a
b
c
d. I use renderer: $.jqplot.CategoryAxisRenderer and it works well, so the ticks show in multiline and
works.

Now I need to rotate them 30º. I tried 'angle: -30' but it doesn't work.

With this config:

xaxis: {
        renderer: $.jqplot.CategoryAxisRenderer,
        tickRenderer: $.jqplot.CanvasAxisTickRenderer ,
        ticks: ['a <br> b <br> c <br> d' , 'p <br> q <br> r <br> s'],
        tickOptions:{
                angle: -30,
                fontSize: '9px'
        }

}

The ticks are shown in one single, rotated, long line. Neither
nor \n are being interpreted as I need. This is the best approach I have found.

Is there any solution for this? How could I write rotated text ticks?

Any suggestion would be very helpful for me. Thanks in advance. Best regards