Unexpected result converting to canonical type

Decimal m = ucum.convert(new Decimal("1",15), "[mi_i]","m");
System.out.println("one mile = " + m + "m expect 1609.344");

Internally convert() first correctly converts 1[mi_i] to canonical unit [m] as 1609.344 but the
conversion from canonical [m] to destination type [m] converts 1609.344 to 1609 because
the identity conversion m->m uses Decimal("1",precision=1)

I would expect the unity conversion to be a noop.