S16-io/watch.t throws false positives

[niner]

nine@sphinx:~/rakudo (master=)> while perl6 -Ilib t/spec/S16-io/watch.t  ; do true ; done
1..1
ok 1 - all watch events received
1..1
ok 1 - all watch events received
1..1
ok 1 - all watch events received
1..1
ok 1 - all watch events received
1..1
ok 1 - all watch events received
1..1
ok 1 - all watch events received
1..1
ok 1 - all watch events received
1..1
ok 1 - all watch events received
1..1
ok 1 - all watch events received
1..1
ok 1 - all watch events received
1..1
ok 1 - all watch events received
1..1
ok 1 - all watch events received
1..1
not ok 1 - all watch events received
# Failed test 'all watch events received'
# at t/spec/S16-io/watch.t line 43
# expected: '10'
#      got: '9'
# You failed 1 test of 1