diff --git a/libsrc/meshing/meshfunc.cpp b/libsrc/meshing/meshfunc.cpp
index b7d91a14..25a7e8b7 100644
--- a/libsrc/meshing/meshfunc.cpp
+++ b/libsrc/meshing/meshfunc.cpp
@@ -12,10 +12,11 @@ namespace netgen
 
 
   // extern double teterrpow; 
-  MESHING3_RESULT MeshVolume (MeshingParameters & mp, Mesh& mesh3d)
+  MESHING3_RESULT MeshVolume (const MeshingParameters & c_mp, Mesh& mesh3d)
   {
     static Timer t("MeshVolume"); RegionTimer reg(t);
-    
+
+     MeshingParameters mp = c_mp; // copy mp to change them here
      int oldne;
      int meshed;
 
@@ -637,7 +638,7 @@ namespace netgen
 
 
 
-  MESHING3_RESULT OptimizeVolume (MeshingParameters & mp, 
+  MESHING3_RESULT OptimizeVolume (const MeshingParameters & mp, 
 				  Mesh & mesh3d)
     //				  const CSGeometry * geometry)
   {
diff --git a/libsrc/meshing/meshfunc.hpp b/libsrc/meshing/meshfunc.hpp
index 7eaaa238..fdbdef4e 100644
--- a/libsrc/meshing/meshfunc.hpp
+++ b/libsrc/meshing/meshfunc.hpp
@@ -16,13 +16,13 @@ class Mesh;
 // class CSGeometry;
 
 /// Build tet-mesh
-DLL_HEADER MESHING3_RESULT MeshVolume (MeshingParameters & mp, Mesh& mesh3d);
+DLL_HEADER MESHING3_RESULT MeshVolume (const MeshingParameters & mp, Mesh& mesh3d);
 
 /// Build mixed-element mesh
 // MESHING3_RESULT MeshMixedVolume (MeshingParameters & mp, Mesh& mesh3d);
 
 /// Optimize tet-mesh
-DLL_HEADER MESHING3_RESULT OptimizeVolume (MeshingParameters & mp, Mesh& mesh3d);
+DLL_HEADER MESHING3_RESULT OptimizeVolume (const MeshingParameters & mp, Mesh& mesh3d);
 //			       const CSGeometry * geometry = NULL);
 
 DLL_HEADER void RemoveIllegalElements (Mesh & mesh3d);
diff --git a/libsrc/meshing/meshtype.hpp b/libsrc/meshing/meshtype.hpp
index 63e0515b..e52d9840 100644
--- a/libsrc/meshing/meshtype.hpp
+++ b/libsrc/meshing/meshtype.hpp
@@ -1298,7 +1298,7 @@ namespace netgen
     NgArray<MeshSizePoint> meshsize_points;
     
     void (*render_function)(bool) = NULL;
-    void Render(bool blocking = false)
+    void Render(bool blocking = false) const
     {
       if (render_function) 
         (*render_function)(blocking);
diff --git a/libsrc/meshing/python_mesh.cpp b/libsrc/meshing/python_mesh.cpp
index 1428a9cf..16f1b269 100644
--- a/libsrc/meshing/python_mesh.cpp
+++ b/libsrc/meshing/python_mesh.cpp
@@ -1023,7 +1023,7 @@ DLL_HEADER void ExportNetgenMeshing(py::module &m)
                   {
                     MeshingParameters mp;
                     if(other) mp = *other;
-                    CreateMPfromKwargs(mp, kwargs);
+                    CreateMPfromKwargs(mp, kwargs, false);
                     return mp;
                   }), py::arg("mp")=nullptr, meshingparameter_description.c_str())
     .def("__str__", &ToString<MP>)
diff --git a/libsrc/meshing/python_mesh.hpp b/libsrc/meshing/python_mesh.hpp
index 45a2b9aa..cbcda74e 100644
--- a/libsrc/meshing/python_mesh.hpp
+++ b/libsrc/meshing/python_mesh.hpp
@@ -80,7 +80,7 @@ elsizeweight: float = 0.2
 
 )delimiter";
 
-  inline void CreateMPfromKwargs(MeshingParameters& mp, py::kwargs kwargs)
+inline void CreateMPfromKwargs(MeshingParameters& mp, py::kwargs kwargs, bool throw_if_not_all_parsed=true)
   {
     if(kwargs.contains("optimize3d"))
       mp.optimize3d = py::cast<string>(kwargs.attr("pop")("optimize3d"));
@@ -165,6 +165,10 @@ elsizeweight: float = 0.2
     if(kwargs.contains("autozrefine"))
       mp.autozrefine = py::cast<bool>(kwargs.attr("pop")("autozrefine"));
     if(kwargs.size())
-      mp.geometrySpecificParameters = make_any<py::kwargs>(std::move(kwargs));
+    {
+      if(throw_if_not_all_parsed)
+        throw Exception(string("Not all kwargs given to GenerateMesh could be parsed:") + string(py::str(kwargs)));
+      mp.geometrySpecificParameters = kwargs;
+    }
   }
 } // namespace netgen
diff --git a/libsrc/stlgeom/meshstlsurface.cpp b/libsrc/stlgeom/meshstlsurface.cpp
index f6bfc411..8e32fd81 100644
--- a/libsrc/stlgeom/meshstlsurface.cpp
+++ b/libsrc/stlgeom/meshstlsurface.cpp
@@ -13,9 +13,8 @@
 namespace netgen
 {
 
-static void STLFindEdges (STLGeometry & geom,
-			  class Mesh & mesh,
-                          MeshingParameters& mparam)
+static void STLFindEdges (STLGeometry & geom, Mesh & mesh,
+                          const MeshingParameters& mparam)
 {
   double h = mparam.maxh;
 
@@ -230,11 +229,11 @@ static void STLFindEdges (STLGeometry & geom,
 
 
 
-void STLSurfaceMeshing1 (STLGeometry & geom, class Mesh & mesh, MeshingParameters& mparam,
+void STLSurfaceMeshing1 (STLGeometry & geom, class Mesh & mesh, const MeshingParameters& mparam,
 			 int retrynr);
 
 
-int STLSurfaceMeshing (STLGeometry & geom, class Mesh & mesh, MeshingParameters& mparam)
+int STLSurfaceMeshing (STLGeometry & geom, class Mesh & mesh, const MeshingParameters& mparam)
 {
   PrintFnStart("Do Surface Meshing");
 
@@ -527,8 +526,8 @@ int STLSurfaceMeshing (STLGeometry & geom, class Mesh & mesh, MeshingParameters&
 
 
 void STLSurfaceMeshing1 (STLGeometry & geom,
-			 class Mesh & mesh,
-                         MeshingParameters& mparam,
+			 Mesh & mesh,
+                         const MeshingParameters& mparam,
 			 int retrynr)
 {
   static int timer1 = NgProfiler::CreateTimer ("STL surface meshing1");
@@ -742,8 +741,8 @@ void STLSurfaceMeshing1 (STLGeometry & geom,
 
 
 void STLSurfaceOptimization (STLGeometry & geom,
-			     class Mesh & mesh,
-			     MeshingParameters & mparam)
+			     Mesh & mesh,
+			     const MeshingParameters & mparam)
 {
   PrintFnStart("optimize STL Surface");
 
diff --git a/libsrc/stlgeom/python_stl.cpp b/libsrc/stlgeom/python_stl.cpp
index e61ec46b..180b5e56 100644
--- a/libsrc/stlgeom/python_stl.cpp
+++ b/libsrc/stlgeom/python_stl.cpp
@@ -194,36 +194,28 @@ DLL_HEADER void ExportSTL(py::module & m)
                              MeshingParameters* pars, py::kwargs kwargs)
                          {
                            MeshingParameters mp;
-                           {
-                             py::gil_scoped_acquire aq;
+                           { py::gil_scoped_acquire aq;
                              STLParameters stlparam;
                              if(pars)
                              {
                                if(pars->geometrySpecificParameters.has_value() &&
                                   (pars->geometrySpecificParameters.type() == typeid(py::kwargs)))
                                {
-                                 py::gil_scoped_acquire aq;
-                                 py::kwargs mp_kwargs = any_cast<py::kwargs>(pars->geometrySpecificParameters);
+                                 auto mp_kwargs = any_cast<py::kwargs>(pars->geometrySpecificParameters);
                                  py::print("geometry specific kwargs:", mp_kwargs);
                                  CreateSTLParametersFromKwargs(stlparam, mp_kwargs);
                                  pars->geometrySpecificParameters.reset();
                                }
                                mp = *pars;
                              }
-                             CreateMPfromKwargs(mp, kwargs);
                              CreateSTLParametersFromKwargs(stlparam, kwargs);
-                             if(kwargs.size())
-                             {
-                               cout << "WARNING: Given meshing arguments that are ignored:";
-                               for(auto& key : kwargs)
-                                 py::print(key);
-                             }
+                             CreateMPfromKwargs(mp, kwargs); // this will throw if any kwargs are not passed
                              mp.geometrySpecificParameters = stlparam;
                            }
                            auto mesh = make_shared<Mesh>();
-                           SetGlobalMesh(mesh);
                            mesh->SetGeometry(geo);
                            ng_geometry = geo;
+                           SetGlobalMesh(mesh);
                            geo->GenerateMesh(mesh,mp);
                            return mesh;
                          }, py::arg("mp") = nullptr,
diff --git a/libsrc/stlgeom/stlgeom.cpp b/libsrc/stlgeom/stlgeom.cpp
index 31c512b3..dd5694df 100644
--- a/libsrc/stlgeom/stlgeom.cpp
+++ b/libsrc/stlgeom/stlgeom.cpp
@@ -14,14 +14,10 @@ int usechartnormal = 1;
 
 void STLMeshing (STLGeometry & geom,
 		 Mesh & mesh,
-                 const MeshingParameters& mparam)
+                 const MeshingParameters& mparam,
+                 const STLParameters& stlpar)
 {
   geom.Clear();
-  STLParameters stlpar = stlparam;
-  if(mparam.geometrySpecificParameters.has_value() && mparam.geometrySpecificParameters.type().name() == typeid(STLParameters).name())
-  {
-    stlpar = any_cast<STLParameters>(mparam.geometrySpecificParameters);
-  }
   geom.BuildEdges(stlpar);
   geom.MakeAtlas(mesh, mparam, stlpar);
   if (multithread.terminate) { return; }
@@ -101,7 +97,12 @@ void STLGeometry :: Save (string filename) const
 
 int STLGeometry :: GenerateMesh (shared_ptr<Mesh> & mesh, MeshingParameters & mparam)
 {
-  return STLMeshingDummy (this, mesh, mparam);
+  STLParameters stlpar = stlparam;
+  if(mparam.geometrySpecificParameters.has_value() && mparam.geometrySpecificParameters.type().name() == typeid(STLParameters).name())
+  {
+    stlpar = any_cast<STLParameters>(mparam.geometrySpecificParameters);
+  }
+  return STLMeshingDummy (this, mesh, mparam, stlpar);
 }
 
 
diff --git a/libsrc/stlgeom/stlgeom.hpp b/libsrc/stlgeom/stlgeom.hpp
index 5e1ecc27..05b03fd8 100644
--- a/libsrc/stlgeom/stlgeom.hpp
+++ b/libsrc/stlgeom/stlgeom.hpp
@@ -40,7 +40,7 @@ namespace netgen
   }
   */
   
-  extern DLL_HEADER MeshingParameters mparam;
+// extern DLL_HEADER MeshingParameters mparam;
   
 
 
@@ -468,7 +468,8 @@ namespace netgen
 
 
 
-  extern int STLMeshingDummy (STLGeometry* stlgeometry, shared_ptr<Mesh> & mesh, MeshingParameters & mparam);
+extern int STLMeshingDummy (STLGeometry* stlgeometry, shared_ptr<Mesh> & mesh, const MeshingParameters & mparam,
+                            const STLParameters& stlpar);
 
 
 }
diff --git a/libsrc/stlgeom/stlgeommesh.cpp b/libsrc/stlgeom/stlgeommesh.cpp
index 426f7bac..6260e793 100644
--- a/libsrc/stlgeom/stlgeommesh.cpp
+++ b/libsrc/stlgeom/stlgeommesh.cpp
@@ -1345,7 +1345,8 @@ void STLGeometry :: RestrictHChartDistOneChart(int chartnum, NgArray<int>& acttr
 }
 
 
-int STLMeshingDummy (STLGeometry* stlgeometry, shared_ptr<Mesh> & mesh, MeshingParameters & mparam)
+int STLMeshingDummy (STLGeometry* stlgeometry, shared_ptr<Mesh> & mesh, const MeshingParameters & mparam,
+                     const STLParameters& stlparam)
 {
   if (mparam.perfstepsstart > mparam.perfstepsend) return 0;
 
@@ -1372,7 +1373,7 @@ int STLMeshingDummy (STLGeometry* stlgeometry, shared_ptr<Mesh> & mesh, MeshingP
   
       //mesh->DeleteMesh();
  
-      STLMeshing (*stlgeometry, *mesh, mparam);
+      STLMeshing (*stlgeometry, *mesh, mparam, stlparam);
 
       stlgeometry->edgesfound = 1;
       stlgeometry->surfacemeshed = 0;
@@ -1471,13 +1472,14 @@ int STLMeshingDummy (STLGeometry* stlgeometry, shared_ptr<Mesh> & mesh, MeshingP
 	      mesh -> LoadLocalMeshSize (mparam.meshsizefilename);	      
 	      mesh -> CalcLocalHFromSurfaceCurvature (mparam.grading, 
 						      stlparam.resthsurfmeshcurvfac);
-	      mparam.optimize2d = "cmsmSm";
-	      STLSurfaceOptimization (*stlgeometry, *mesh, mparam);
+              MeshingParameters mpar = mparam;
+	      mpar.optimize2d = "cmsmSm";
+	      STLSurfaceOptimization (*stlgeometry, *mesh, mpar);
 #ifdef STAT_STREAM
 	      (*statout) << GetTime() << " & ";
 #endif
 
-	      mparam.Render();
+	      mpar.Render();
 	    }
 	  stlgeometry->surfaceoptimized = 1;
 	}
diff --git a/libsrc/stlgeom/stlpkg.cpp b/libsrc/stlgeom/stlpkg.cpp
index 1372702f..7864a688 100644
--- a/libsrc/stlgeom/stlpkg.cpp
+++ b/libsrc/stlgeom/stlpkg.cpp
@@ -21,6 +21,7 @@ namespace netgen
 {
   DLL_HEADER extern shared_ptr<NetgenGeometry>  ng_geometry;
   DLL_HEADER extern shared_ptr<Mesh> mesh;
+  DLL_HEADER extern MeshingParameters mparam;
 
   static VisualSceneSTLGeometry vsstlgeom;
   static VisualSceneSTLMeshing vsstlmeshing;
diff --git a/libsrc/stlgeom/stltool.hpp b/libsrc/stlgeom/stltool.hpp
index f617d275..4464bac1 100644
--- a/libsrc/stlgeom/stltool.hpp
+++ b/libsrc/stlgeom/stltool.hpp
@@ -278,17 +278,18 @@ DLL_HEADER extern STLParameters stlparam;
 
 
 void STLMeshing (STLGeometry & geom,
-		 class Mesh & mesh,
-                 const MeshingParameters& mparam);
+		 Mesh & mesh,
+                 const MeshingParameters& mparam,
+                 const STLParameters& stlpar);
 
 
 int STLSurfaceMeshing (STLGeometry & geom,
-                       class Mesh & mesh,
-                       MeshingParameters& mparam);
+                       Mesh & mesh,
+                       const MeshingParameters& mparam);
 
 void STLSurfaceOptimization (STLGeometry & geom,
-			     class Mesh & mesh,
-			     class MeshingParameters & mparam);
+			     Mesh & mesh,
+			     const MeshingParameters & mparam);
 
 
 
diff --git a/nglib/nglib.cpp b/nglib/nglib.cpp
index e44b58c4..293cfa55 100644
--- a/nglib/nglib.cpp
+++ b/nglib/nglib.cpp
@@ -30,6 +30,8 @@ namespace netgen {
    extern void MeshFromSpline2D (SplineGeometry2d & geometry,
                                  shared_ptr<Mesh> & mesh, 
                                  MeshingParameters & mp);
+   extern MeshingParameters mparam;
+   extern STLParameters stlparam;
 }
 
 
@@ -667,7 +669,7 @@ namespace nglib
         }
       */
 
-      STLMeshing (*stlgeometry, *me, mparam);
+      STLMeshing (*stlgeometry, *me, mparam, stlparam);
 
       stlgeometry->edgesfound = 1;
       stlgeometry->surfacemeshed = 0;