Improper highlighting of custom HTML tags that contain hyphens

[lutalli]

When I write custom HTML tags in a Markdown file that contain hyphens (like <my-tag></my-tag>), the highlighting works in a wrong way: The words connected by hyphens are highlighted individually, which leads to that, if a word in my custom tag is identical to a standard HTML tag, it's highlighted differently:

Instead, a tag with hyphens should be treated as whole:

I'm not sure if this is a bug of this plugin, but I'm not experiencing this bug while working in an HTML file.