what is na?

[Billy Patton]

I've been writing my XS on the sun with version 5.005
This line is ok on the sun, but fails on my PC runniing
perl 5.6.1
    name = (char*) SvPV(*av_fetch(a,i,0),na);

perlguts tell me I can use SvPV_nolen with 5.6
but perl5 does not recognize this.
What #ifdef can I use to put into my XS
#ifdef XXX
    name = (char*) SvPV(*av_fetch(a,i,0),na);
#else
    name = (char*) SvPV_nolen(*av_fetch(a,i,0));
#endif