You can use the --hex-charset option to specify this set of binary.
Edit: specifically, something like:
--hex-charset -1 000102030405060708 ?1?1?1?1?1?1?1?1
... or however long your expected strings are.
Edit: specifically, something like:
--hex-charset -1 000102030405060708 ?1?1?1?1?1?1?1?1
... or however long your expected strings are.
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