diff --git a/libsrc/stlgeom/python_stl.cpp b/libsrc/stlgeom/python_stl.cpp
index 0ab54822..1220f133 100644
--- a/libsrc/stlgeom/python_stl.cpp
+++ b/libsrc/stlgeom/python_stl.cpp
@@ -4,6 +4,12 @@
 #include <../general/ngpython.hpp>
 #include <stlgeom.hpp>
 
+#ifdef WIN32
+   #define DLL_HEADER   __declspec(dllexport)
+#else
+   #define DLL_HEADER 
+#endif
+
 using namespace netgen;
 namespace netgen
 {
diff --git a/libsrc/stlgeom/vsstl.cpp b/libsrc/stlgeom/vsstl.cpp
index 60011f61..2cb7b9e4 100644
--- a/libsrc/stlgeom/vsstl.cpp
+++ b/libsrc/stlgeom/vsstl.cpp
@@ -1214,6 +1214,14 @@ void VisualSceneSTLMeshing :: MouseDblClick (int px, int py)
 
 
 #ifdef NG_PYTHON
+
+
+#ifdef WIN32
+   #define DLL_HEADER   __declspec(dllexport)
+#else
+   #define DLL_HEADER 
+#endif
+
 #include <../general/ngpython.hpp>
 
 DLL_HEADER void ExportSTLVis(py::module &m)