password to SMPP too long

I'm using kannel 1.3.2 development release. My SMPP provider gave me a
9 character password but kannel only supports 8.
When I changed smpp_pdu.def it worked (diff):
125c125
<     NULTERMINATED(password, 9)
---
>     NULTERMINATED(password, 10)

Is the length due to some standardcompliance or is it arbitrary?
Would there be any problems if this was changed even if the
standard says 8 characters?

Best regards
Robert Andersson