Weird dmd error?

[Andrea Fontana via Digitalmars-d]

--- test.d
void* test (ssize_t );
import core.sys.posix.unistd;
---

Try to run:
dmd test.d

It says:
/usr/include/dmd/druntime/import/core/sys/posix/sys/types.d(100): 
Error: undefined identifier 'c_long'