Why is request.getRemoteUser() returning the tomcat windows service account sometimes

I'm trying to get windows authentification to work with a 3rd party application developped with GWT. I'm hosting the app with tomcat, on a windows server. I access the site through an IIS proxy (installed following the tomcat's documentation).

If i modify a .jsp of the webapp to display "<%= request.getRemoteUser() %>" , I get the useame i'm hopping for, my windows account.

But the webapp authenticate me with the account I installed the Tomcat windows service with on the server.

In the (decompiled) source code of the webapp, i see a call to the exact same "request.getRemoteUser()" , so I wonder where can be the difference.

Here are the decompiled classes :

import javax.servlet.http.HttpServletRequest;

public class RemoteUserLoginProvider
  extends BaseRequestLoginProvider
{
  public String extractLoginFromRequest(HttpServletRequest request)
  {
    retu request.getRemoteUser();
  }
}

And :

import com.google.inject.Inject;
import com.google.inject.Provider; 
import javax.servlet.http.HttpServletRequest;

public abstract class BaseRequestLoginProvider
  implements Provider<String>
{
  @Inject
  private Provider<HttpServletRequest> requestProvider;
  @Inject(optional=true)

  public abstract String extractLoginFromRequest(HttpServletRequest paramHttpServletRequest);

  public String get()
  {
    HttpServletRequest request = (HttpServletRequest)this.requestProvider.get();
    String userlogin = extractLoginFromRequest(request);

    retu userlogin;
  }
}

Could my problem be linked to this bug on google's guice : https://github.com/google/guice/issues/780 ?

If so, is there any work around ?