Is there a way to connect a signal of a MDISubWindow to a slot in a main window? I have something like this:

Qt Code: 
  1. connect(fvui.closePBpvf, SIGNAL(clicked()), nnDBSMainWindow, SLOT(closeActiveSubWindow()));
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But I keep getting the compilation error: src/nnDBSPieceViewForm.cpp:27: error: ‘nnDBSMainWindow’ was not declared in this scope

I then tried adding #include "nnDBSMainWindow.h" to the form, but now I get the compilation error: src/nnDBSPieceViewForm.cpp:28: error: expected primary-expression before ‘,’ token

Can someone help me out please? Thanks in advance!