diff --git a/include/wx/generic/busyinfo.h b/include/wx/generic/busyinfo.h
index c9a5a2c8cc..feaa431831 100644
--- a/include/wx/generic/busyinfo.h
+++ b/include/wx/generic/busyinfo.h
@@ -15,6 +15,7 @@
 #if wxUSE_BUSYINFO
 
 class WXDLLIMPEXP_FWD_CORE wxFrame;
+class WXDLLIMPEXP_FWD_CORE wxWindow;
 
 //--------------------------------------------------------------------------------
 // wxBusyInfo