Error with modules?

[Alexey Ryaboshapko]

Hi. 
I have following idl text:
//file a.idl
module A {
  interface B {
    void f();
    };
  };

It's compiled by omniidl2.exe into two files a.cpp and a.h
after that I'm trying to compile it with MSVC5.0 to a.obj file,
the following error messages come:
CL /GR /nologo /MD /W3 /GX /O2 /D "WIN32" /D "_CONSOLE" /D "__NT__" /D "
_X86_" -I. -Id:\omniORB2\include -c a.CPP
a.CPP
a.h(153) : error C2027: use of undefined type 'A'
a.h(160) : error C2027: use of undefined type 'A'
NMAKE : fatal error U1077: 'CL' : return code '0x2'
Stop.

What I have to do?
Am I wrong?