previous/next post link: get arrows inside

Hey,

I could use some help with the post-navigation-links in wordpress. I included the previous/next post links on the post-page of my theme, like so:

<ul class="postnavi">
                <li class="zurueckLink"><?php previous_post_link('« %link'); ?></li>
                <li class="weiterLink"><?php next_post_link('%link »'); ?></li>
            </ul>

This is the HTML, that I get from that:

<li class="zurueckLink">« <a rel="prev" href="http://corvinweber.de/?p=7">Tweet from XXXX</a></li>

The arrow is outside of the anchor-tag, but I’d like it within. Is there a way to get it inside?