Markdown on Save Improved adding paragraph tags to custom css stylesheet

When I try and save my custom css inside the Custom CSS editor, Markdown on Save Improved adds paragraphs tags.

It results in a css file that looks like this:

<p>/*
Welcome to Custom CSS!</p>

<p>CSS (Cascading Style Sheets) is a kind of code that tells the browser how
to render a web page. You may delete these comments and get started with
your customizations.</p>

<p>By default, your stylesheet will be loaded after the theme stylesheets,
which means that your rules can take precedence and override the theme CSS
rules. Just write here what you want to change, you don't need to copy all
your theme's stylesheet content.
<em>/
/</em> Generic changes meant to effect the entire site. */
ul {
    list-style-type: circle;
}</p>

<p>/* Changes to the nav bar */
.current_page_item a {
    color: #ff9c10;
}</p>

<p>.current_page_item a:hover {
    color: #ff8c00;
}</p>

Obviously, this won’t run. What can I do to resolve this issue?

Related thread:

http://wordpress.org/extend/plugins/markdown-on-save-improved/