EPUB3 not supported

[legowerewolf]

Log:

Starting job: https://standardebooks.org/ebooks/abraham-merritt/the-moon-pool/dist/abraham-merritt_the-moon-pool.epub3 
Job: "https://standardebooks.org/ebooks/abraham-merritt/the-moon-pool/dist/abraham-merritt_the-moon-pool.epub3" failed with error: 
Traceback (most recent call last):
  File "site-packages\calibre\gui2\threaded_jobs.py", line 83, in start_work
  File "site-packages\calibre\gui2\ebook_download.py", line 87, in __call__
  File "site-packages\calibre\gui2\ebook_download.py", line 109, in _add
Exception: Not a support e-book format.
 
Called with args: (<calibre.gui2.ui.Main object at 0x00000188486F9678>, None, u'https://standardebooks.org/ebooks/abraham-merritt/the-moon-pool/dist/abraham-merritt_the-moon-pool.epub3', u'', u'', True, [], None) {u'abort': <threading._Event object at 0x000001884D1F49C8>, u'log': <calibre.utils.logging.GUILog object at 0x000001884D1F4C88>, u'notifications': <Queue.Queue instance at 0x000001884D1F4848>} 

Attempting to grab from the Standard Ebooks OPDS feed