diff --git a/include/wx/iosfwrap.h b/include/wx/iosfwrap.h
index 4d3efed221..78ad8d53b7 100644
--- a/include/wx/iosfwrap.h
+++ b/include/wx/iosfwrap.h
@@ -18,5 +18,9 @@
 #   include <iosfwd>
 #endif
 
+#ifdef __WXMSW__
+#   include "wx/msw/winundef.h"
+#endif
+
 #endif // wxUSE_STD_IOSTREAM
 
diff --git a/include/wx/ioswrap.h b/include/wx/ioswrap.h
index 8fb05a1579..6fe41e556b 100644
--- a/include/wx/ioswrap.h
+++ b/include/wx/ioswrap.h
@@ -17,6 +17,10 @@
 #   include <iostream>
 #endif
 
+#ifdef __WXMSW__
+#   include "wx/msw/winundef.h"
+#endif
+
 #endif
   // wxUSE_STD_IOSTREAM