how to rid red border of html labels in mxGraph/JGraph used in a toolwindow

Hi,

I am using mxGraph to render a graph in a toolwindow.

this.graph = new mxGraph();

// ... adding cells and edges

this.graph.setHtmlLabels(true);

I need to be able to show labels with bold sections, so I enabled HTML labels in the whole graph. But the rendered graph has red borders for all the labels. I tested a standalone mxGraph, and the HTML labels can be displayed properly without the red borders.

If I disable HTML labels, the red borders will be gone, but the bold fonts cannot be displayed either.

Are these borders added by IntelliJ or something else? I tried set styles in mxGraph, but couldn't resolve this problem. Please help.