Stanc could not find include file

Interfaces RStan
5

Very simple, failing example attached, main stan program and file containing function are both in the directory in which R is being run:

myfunc.stan (56 Bytes)
mymain.stan (46 Bytes)

attempted compilation:

ff <- stanc("mymain.stan")
could not find include file: #include myfunc.stan
Error in stanc("mymain.stan") :
  failed to parse Stan model 'mymain' due to the above error.

Thanks for taking a look at this. I’m stumped.