diff --git a/docs/doxygen/mainpages/const_cpp.h b/docs/doxygen/mainpages/const_cpp.h
index cf3bacf7ab..919e0c54c4 100644
--- a/docs/doxygen/mainpages/const_cpp.h
+++ b/docs/doxygen/mainpages/const_cpp.h
@@ -401,6 +401,9 @@ more details.
         defined when compiling code which uses wxWidgets as a DLL/shared library}
 @itemdef{WXBUILDING,
         defined when building wxWidgets itself, whether as a static or shared library}
+@itemdef{wxICON_IS_BITMAP,
+         defined in the ports where wxIcon inherits from wxBitmap (all but
+         wxMSW currently)}
 @endDefList
 
 */
diff --git a/include/wx/icon.h b/include/wx/icon.h
index 0849ab98b8..27dc369141 100644
--- a/include/wx/icon.h
+++ b/include/wx/icon.h
@@ -25,6 +25,8 @@
 #if defined(__WXMSW__)
   #define wxICON_DEFAULT_TYPE   wxBITMAP_TYPE_ICO_RESOURCE
   #include "wx/msw/icon.h"
+
+  #define wxICON_DIFFERENT_FROM_BITMAP
 #elif defined(__WXMOTIF__)
   #define wxICON_DEFAULT_TYPE   wxBITMAP_TYPE_XPM
   #include "wx/motif/icon.h"
@@ -58,6 +60,10 @@
   #include "wx/generic/icon.h"
 #endif
 
+#ifndef wxICON_DIFFERENT_FROM_BITMAP
+    #define wxICON_IS_BITMAP
+#endif
+
 //-----------------------------------------------------------------------------
 // wxVariant support
 //-----------------------------------------------------------------------------