MmFile : Is this std.mmFile BUG?

[Junichi Nakata via Digitalmars-d-learn]

Hi, all.
I have a question.
When 'testdic' file does' t exist, something  wrong.

---
import std.mmFile;

int main() {
   auto x = new MmFile("testdic",MmFile.Mode.readWrite,0,null);
   return 0;
}

---
OSX 10.10.3 ,
DMD64 D Compiler v2.069-devel-d0327d9

After testdic file (size=0) was made, Segmentation Fault: 11 .

I don't know whether this code is typical use.
Is this Phobos BUG? or BY DESIGN?