Scrap a form on incorrect web page

I'm trying to scrap a webform using robobrowser with python 3.4. I use the default html parser:

self._browser = RoboBrowser(history=True, parser="html.parser")

It works fine for correct web pages but now I have to parse incorrectly written page. Here is the html fragment:

<form method="post"  action="decide.php?act=submit_advance">
    <table  class="td_advanced">
    <tr class="td_advance">
    <td colspan="4" class="td_advance"></strong><br></td>
    <td colspan="3" class="td_left">Case sensitive:<br><br></td>
    <td><input type="checkbox" name="case_sensitive" /><br><br></td>
[...]
</form>

The closing strong tag is incorrect. This error prevents the parser from read all inputs following this incorrect tag:

form = self._browser.get_form()
print(form)
>>> <RoboForm>

Any suggestions?