[hashcash] Procmail Problem

Since upgrading to hashcash-1.16, I've become aware of an issue with
hashcash not validating the token when executed through procmail.
Unfortunately I upgraded from v1.13 so I'm not exactly sure when the
problem was introduced, or even if it is a hashcash problem or something
else.

Procmail Recipe:
:0
* ^X-Hashcash:
* $? hashcash -cqXdp 1d -b24 -f $HOME/hashcash/hashcash.db -r testing
| ~mail2news/bin/multipost

When I fire an Email through this recipe, I get the following log:
procmail: Match on "^X-Hashcash:"
procmail: Executing 
"hashcash,-cqXdp,1d,-b24,-f,/home/mail2news/hashcash/hashcash.db,-r,testing"
procmail: Match on "hashcash -cqXdp 1d -b24 -f 
/home/mail2news/hashcash/hashcash.db -r testing"
procmail: Executing " ~mail2news/bin/multipost"

The Hashcash header on the Email is:
X-Hashcash: foobar

Nothing is logged in the hashcash.db for this message, which suggests
that hashcash rejects the invalid header, but the procmail action is
executed.  Any suggestions what might be causing this?

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