diff --git a/src/Mod/Fem/App/FemPostFilterPyImp.cpp b/src/Mod/Fem/App/FemPostFilterPyImp.cpp
index 3b27e3bf2d..7cac967a01 100644
--- a/src/Mod/Fem/App/FemPostFilterPyImp.cpp
+++ b/src/Mod/Fem/App/FemPostFilterPyImp.cpp
@@ -56,44 +56,49 @@ PyObject* FemPostFilterPy::addFilterPipeline(PyObject* args)
     const char* name;
     PyObject* source = nullptr;
     PyObject* target = nullptr;
-
-    if (PyArg_ParseTuple(args, "sOO", &name, &source, &target)) {
-
-        // extract the algorithms
-        vtkObjectBase* obj = vtkPythonUtil::GetPointerFromObject(source, "vtkAlgorithm");
-        if (!obj) {
-            // error marker is set by PythonUtil
-            return nullptr;
-        }
-        auto source_algo = static_cast<vtkAlgorithm*>(obj);
-
-        obj = vtkPythonUtil::GetPointerFromObject(target, "vtkAlgorithm");
-        if (!obj) {
-            // error marker is set by PythonUtil
-            return nullptr;
-        }
-        auto target_algo = static_cast<vtkAlgorithm*>(obj);
-
-        // add the pipeline
-        FemPostFilter::FilterPipeline pipe;
-        pipe.source = source_algo;
-        pipe.target = target_algo;
-        getFemPostFilterPtr()->addFilterPipeline(pipe, name);
+    PyTypeObject* typeAlgo = vtkPythonUtil::FindClassTypeObject("vtkAlgorithm");
+    if (!PyArg_ParseTuple(args, "sO!O!", &name, typeAlgo, &source, typeAlgo, &target)) {
+        return nullptr;
     }
+
+    // extract the algorithms
+    vtkObjectBase* obj = vtkPythonUtil::GetPointerFromObject(source, "vtkAlgorithm");
+    if (!obj) {
+        // error marker is set by PythonUtil
+        return nullptr;
+    }
+    auto source_algo = static_cast<vtkAlgorithm*>(obj);
+
+    obj = vtkPythonUtil::GetPointerFromObject(target, "vtkAlgorithm");
+    if (!obj) {
+        // error marker is set by PythonUtil
+        return nullptr;
+    }
+    auto target_algo = static_cast<vtkAlgorithm*>(obj);
+
+    // add the pipeline
+    FemPostFilter::FilterPipeline pipe;
+    pipe.source = source_algo;
+    pipe.target = target_algo;
+    getFemPostFilterPtr()->addFilterPipeline(pipe, name);
+
     Py_Return;
 #else
+    (void)args;
     PyErr_SetString(PyExc_NotImplementedError, "VTK python wrapper not available");
-    Py_Return;
+    return nullptr;
 #endif
 }
 
 PyObject* FemPostFilterPy::setActiveFilterPipeline(PyObject* args)
 {
     const char* name;
-    if (PyArg_ParseTuple(args, "s", &name)) {
-        getFemPostFilterPtr()->setActiveFilterPipeline(std::string(name));
+    if (!PyArg_ParseTuple(args, "s", &name)) {
+        return nullptr;
     }
 
+    getFemPostFilterPtr()->setActiveFilterPipeline(std::string(name));
+
     Py_Return;
 }
 
@@ -109,7 +114,7 @@ PyObject* FemPostFilterPy::getParentPostGroup(PyObject* args)
         return group->getPyObject();
     }
 
-    return Py_None;
+    Py_Return;
 }
 
 PyObject* FemPostFilterPy::getInputData(PyObject* args)
@@ -133,17 +138,18 @@ PyObject* FemPostFilterPy::getInputData(PyObject* args)
         default:
             PyErr_SetString(PyExc_TypeError,
                             "cannot return datatype object; not unstructured grid");
-            Py_Return;
+            return nullptr;
     }
 
     // return the python wrapper
     copy->DeepCopy(dataset);
     PyObject* py_dataset = vtkPythonUtil::GetObjectFromPointer(copy);
 
-    return Py::new_reference_to(py_dataset);
+    return py_dataset;
 #else
+    (void)args;
     PyErr_SetString(PyExc_NotImplementedError, "VTK python wrapper not available");
-    Py_Return;
+    return nullptr;
 #endif
 }
 
@@ -196,10 +202,11 @@ PyObject* FemPostFilterPy::getOutputAlgorithm(PyObject* args)
     auto algorithm = getFemPostFilterPtr()->getFilterOutput();
     PyObject* py_algorithm = vtkPythonUtil::GetObjectFromPointer(algorithm);
 
-    return Py::new_reference_to(py_algorithm);
+    return py_algorithm;
 #else
+    (void)args;
     PyErr_SetString(PyExc_NotImplementedError, "VTK python wrapper not available");
-    Py_Return;
+    return nullptr;
 #endif
 }
 
diff --git a/src/Mod/Fem/App/FemPostObjectPyImp.cpp b/src/Mod/Fem/App/FemPostObjectPyImp.cpp
index 50cd7184d9..95b6e2482e 100644
--- a/src/Mod/Fem/App/FemPostObjectPyImp.cpp
+++ b/src/Mod/Fem/App/FemPostObjectPyImp.cpp
@@ -69,12 +69,14 @@ PyObject* FemPostObjectPy::getDataSet(PyObject* args)
     auto dataset = getFemPostObjectPtr()->getDataSet();
     if (dataset) {
         PyObject* py_algorithm = vtkPythonUtil::GetObjectFromPointer(dataset);
-        return Py::new_reference_to(py_algorithm);
+        return py_algorithm;
     }
-    return Py_None;
-#else
-    PyErr_SetString(PyExc_NotImplementedError, "VTK python wrapper not available");
+
     Py_Return;
+#else
+    (void)args;
+    PyErr_SetString(PyExc_NotImplementedError, "VTK python wrapper not available");
+    return nullptr;
 #endif
 }
 
diff --git a/src/Mod/Fem/App/FemPostPipelinePyImp.cpp b/src/Mod/Fem/App/FemPostPipelinePyImp.cpp
index 556a0ca5f5..919952da01 100644
--- a/src/Mod/Fem/App/FemPostPipelinePyImp.cpp
+++ b/src/Mod/Fem/App/FemPostPipelinePyImp.cpp
@@ -327,10 +327,11 @@ PyObject* FemPostPipelinePy::getOutputAlgorithm(PyObject* args)
     auto algorithm = getFemPostPipelinePtr()->getOutputAlgorithm();
     PyObject* py_algorithm = vtkPythonUtil::GetObjectFromPointer(algorithm);
 
-    return Py::new_reference_to(py_algorithm);
+    return py_algorithm;
 #else
+    (void)args;
     PyErr_SetString(PyExc_NotImplementedError, "VTK python wrapper not available");
-    Py_Return;
+    return nullptr;
 #endif
 }
 
diff --git a/src/Mod/Fem/Gui/ViewProviderFemPostFilterPyImp.cpp b/src/Mod/Fem/Gui/ViewProviderFemPostFilterPyImp.cpp
index 9d4cb51253..e152d34d5d 100644
--- a/src/Mod/Fem/Gui/ViewProviderFemPostFilterPyImp.cpp
+++ b/src/Mod/Fem/Gui/ViewProviderFemPostFilterPyImp.cpp
@@ -79,8 +79,9 @@ PyObject* ViewProviderFemPostFilterPy::createExtractionTaskWidget(PyObject* args
     PyErr_SetString(PyExc_TypeError, "creating the panel failed");
     return nullptr;
 #else
+    (void)args;
     PyErr_SetString(PyExc_NotImplementedError, "VTK python wrapper not available");
-    Py_Return;
+    return nullptr;
 #endif
 }