diff --git a/libsrc/stlgeom/stlgeom.hpp b/libsrc/stlgeom/stlgeom.hpp
index 859bee3c..67c23338 100644
--- a/libsrc/stlgeom/stlgeom.hpp
+++ b/libsrc/stlgeom/stlgeom.hpp
@@ -484,7 +484,7 @@ namespace netgen
 
 
 
-extern int STLMeshingDummy (STLGeometry* stlgeometry, shared_ptr<Mesh> & mesh, const MeshingParameters & mparam,
+DLL_HEADER extern int STLMeshingDummy (STLGeometry* stlgeometry, shared_ptr<Mesh> & mesh, const MeshingParameters & mparam,
                             const STLParameters& stlpar);