Symbol undefined due to import statement

[Andre]

Hi,
there is a behaviour which seems strange for me.
I have following structure

C:\Projects\ProjectA\main.d
C:\Projects\Reusuable\net\http.d

The content of main.d is:
  module main;

  import std.stdio;
  import net.http;

  int main()
  {
	return 0;
  }

The content of http.d is:
  module net.http;

I compile the application with command:
dmd -IC:\Projects\Reusuable main.d

This works, but if I now edit the http.d file
and add an import statement like "import std.stdio;"
then the linker will output following error:

  main.obj(main)
  Error 42: Symbol Undefined _D3net4http12__ModuleInfoZ

Where is my error?

Kind regards
Andre