Sequence diagram: word 'Participant' causes an exception

[kongakong]

If you add a line Bob-->Participant: I am good thanks! to tests/fixtures/sequence/simple.sequence,

i.e.

Alice->Bob: Hello Bob, how are you?
Note right of Bob: Bob thinks
Bob-->Participant: I am good thanks!
Bob-->Alice: I am good thanks!

then run ./bin/diagrams.js sequence tests/fixtures/sequence/simple.sequence

you will get this error

sequence:stdout: Parse error on line 3:
...b: Bob thinksBob-->Participant: I am go
----------------------^
Expecting 'ACTOR', got 'participant'

sequence:stderr: Parse error on line 3:
...b: Bob thinksBob-->Participant: I am go
----------------------^
Expecting 'ACTOR', got 'participant'

If you change Participant to something else like Tom, it works again.