diff --git a/libsrc/interface/nginterface.cpp b/libsrc/interface/nginterface.cpp
index 33220257..56fae671 100644
--- a/libsrc/interface/nginterface.cpp
+++ b/libsrc/interface/nginterface.cpp
@@ -109,8 +109,13 @@ namespace netgen
 {
 #include "writeuser.hpp"
 
+#ifndef WIN32
   shared_ptr<Mesh> mesh;
   shared_ptr<NetgenGeometry> ng_geometry;
+#else
+  extern shared_ptr<Mesh> mesh;
+  extern shared_ptr<NetgenGeometry> ng_geometry;
+#endif
 
 #ifndef NOTCL
   extern Tcl_Interp * tcl_interp;