XmlPullParser doesn't parse correctly attributes with complex namespace

Having a markup like:
<a class="addthis_button_google_plusone_badge" g:plusone:size="smallbadge" g:plusone:href="https://plus.google.com/25252/"></a> causes XmlPullParser to throw the following exception:

java.text.ParseException: Same attribute found twice: g:plusone (line 19, column 100)
at org.apache.wicket.markup.parser.XmlPullParser.parseTagText(XmlPullParser.java:673)
at org.apache.wicket.markup.parser.XmlPullParser.next(XmlPullParser.java:294)
at org.apache.wicket.markup.parser.filter.RootMarkupFilter.nextElement(RootMarkupFilter.java:58)
.....