+#if wxUSE_BACKINGFILE
+# if !wxUSE_STREAMS || (!wxUSE_FILE && !wxUSE_FFILE)
+# ifdef wxABORT_ON_CONFIG_ERROR
+# error "wxBackingFile requires wxStream and wxFile or wxFFile"
+# else
+# undef wxUSE_BACKINGFILE
+# define wxUSE_BACKINGFILE 0
+# endif
+# endif
+#endif /* wxUSE_BACKINGFILE */
+