Incorrect interpretation of relative and absolute paths with Microdata

Parsing the following fragment located at http://ruben.verborgh.org/tmp/slash-test.html
<a itemprop="url" href="/">Homepage</a>
<a itemprop="url" href="other.html">Other</a>
results in the URIs
http://ruben.verborgh.org/tmp/slash-test.html//
http://ruben.verborgh.org/tmp/slash-test.html/other.html
instead of the correct
http://ruben.verborgh.org/tmp/
http://ruben.verborgh.org/tmp/other.html

Note that there is no trailing slash in the original.

Test case:
http://ruben.verborgh.org/tmp/slash-test.html
http://any23.org/any23/?format=best&uri=http%3A%2F%2Fruben.verborgh.org%2Ftmp%2Fslash-test.html&validation-mode=none