diff --git a/src/proxyface/windoze.hxx b/src/proxyface/windoze.hxx
index ad8e4d4..08e4419 100644
--- a/src/proxyface/windoze.hxx
+++ b/src/proxyface/windoze.hxx
@@ -8,6 +8,9 @@
 #ifndef PROXY_WINDOZE_HXX
 #define PROXY_WINDOZE_HXX
 
+#ifdef DATADIR
+#undef DATADIR
+#endif
 #include <windows.h>
 #include <winhttp.h>