Use arc export --unified to export full diff

I’m trying to use arc export --unified to export a full SVN diff to upload and create a differential revision in our Phabricator instance. The server I’m using does not have a connection to the Phabricator instance, so I cannot simply run arc diff. arc export --unified gives me mostly what I want, but the file that it generates does not include the lines that are unchanged. Is there an option that I can specify so that I can include these lines?