Problem with context filter, --context-visible-first, and zeros

I am having a problem with the context filter. When 
--context-visible-first is set, a 0 within an invisible context will 
cause the filter to go back to a visible context. The following testcase 
demonstrates this:

====

cat < test1.txt << __END__
Properly spelled.

aaaaaawrong

/* bbbbbbwrong cccccwrong */

ddddddwrong

Also correct.
__END__

cat < test2.txt << __END__
Properly spelled.

aaaaaawrong

/* bbbbbbwrong 0 cccccwrong */

ddddddwrong

Also correct.
__END__

# this will mark only a and d as misspelled, as expected
aspell --add-filter=context --context-visible-first check test1.txt

# with the addition of the 0, this will also mark c as misspelled
aspell --add-filter=context --context-visible-first check test2.txt