Using DockingPanes in VC6

I think the LNK2001 problems are only happening in code I have in a template class defined entirely in a .H file.

Did something change related to that between the 9.81 version and the 15.0.2 version?

Odd indeed, it's even more since I only replace the #import from 9.81 to the demo 15.0.2.

CustomFilter.obj : error LNK2001: unresolved external symbol "public: short __thiscall XtremeDockingPane::IPane::GetHidden(void)" (?GetHidden@IPane@XtremeDockingPane@@QAEFXZ)
Filter.obj : error LNK2001: unresolved external symbol "public: short __thiscall XtremeDockingPane::IPane::GetHidden(void)" (?GetHidden@IPane@XtremeDockingPane@@QAEFXZ)

My code is something like this (a .H file):

template<class T, class TCtrl>
class ICustomPaneImpl : public ICustomPane
{
     ...
     virtual ECustomPaneMode GetPaneMode()
     {
          if(!m_bInitialized) return epmClosed;
          if(m_pPaneContainer->Closed == VARIANT_TRUE) return epmClosed;
          if(m_pPaneContainer->Hidden == VARIANT_TRUE) return epmLoose;
          return epmDocked;
     }
     ...

Apparently using Hidden, Closed or any other member in the template class makes the compiler unhappy. In another projects it works only when I'm calling the members in .cpp files.

I don't have idea what's going on, maybe you can point me what to look for. All I've changed is the #import, and it was all working with the 9.81 version.