switching between richt text and plain text strips tags that formerly weren't stripped

I just upgraded my drupal install from 7.32 to 7.33. After doing so, when I paste some html in plain text format and switch to rich text format, some tags are getting stripped that didn't get stripped before.
For example:
I paste this into the body text field in plain text format:

<p><a id="IndexA"></a></p>
<p><span class="indexAchter">Aardenborg, van</span> </p>

After switching to rich text format, prior to saving I already notice anchors missing, so I go to plain text format again and see:

<p></p>
<p><span class="indexAchter">Aardenborg, van</span> </p>

Haven't changed any settings and it worked perfectly well before. How do I solve this? I do need my empty anchor tags..

Vincent