Vanguard OFX Import Failing due to negative units

[stin7]

$ python run.py 
...
AssertionError
> .venv/lib/python3.9/site-packages/beancount_import/source/ofx.py(997)get_entries()
-> assert units < ZERO

Looking in the OFX file downloaded from Vanguard, I see entries like this:
<UNIQUEIDTYPE>CUSIP</SECID><SUBACCTSEC>CASH<UNITS>-0.00007<TFERACTION>OUT<POSTYPE>LONG

Any thoughts on how I might try to fix? I'd rather not write a custom importer since I would guess this could be common.