OpenXML: Consecutive runs containing tabs can be incorrectly merged

The attached file contains some text with two embedded tabs, divided across multiple runs. The pattern looks like this:

#!xml

<w:r>
  <w:tab/>
  <w:t>-</w:t>
</w:r>
<w:r>
  <w:tab/>
  <w:t>R</w:t>
</w:r>

Because the runs have the same properties, they are merged, but the tabs are ignored, so you end up with a single run like this:

#!xml

<w:r>
  <w:tab/>
  <w:t>-R</w:t>
</w:r>

The result of this is that one of the tabs appears to disappear during translation.