diff --git a/src/Mod/Part/App/GeometryDefaultExtension.h b/src/Mod/Part/App/GeometryDefaultExtension.h
index d8640eab30..5f983610e7 100644
--- a/src/Mod/Part/App/GeometryDefaultExtension.h
+++ b/src/Mod/Part/App/GeometryDefaultExtension.h
@@ -34,7 +34,7 @@ namespace Part {
     {
         TYPESYSTEM_HEADER();
     public:
-        GeometryDefaultExtension() = default;
+        inline GeometryDefaultExtension();
         GeometryDefaultExtension(const T& val, std::string name = std::string());
         virtual ~GeometryDefaultExtension() = default;
 
@@ -63,7 +63,8 @@ namespace Part {
     //
     // Warnings:
     // - The default constructor relies on the default constructor of T for initialisation. Built-in types
-    //   so constructed will be uninitialised. Use the specific constructor from a T to initiliase it.
+    //   so constructed will be uninitialised. Use the specific constructor from a T to initiliase it. Note
+    //   that the default constructor is required by the type system (see TYPESYSTEM_SOURCE_TEMPLATE_T).
     //
     // Default assumptions:
     // - T can be constructed from T
@@ -85,6 +86,19 @@ namespace Part {
     // 5. Provide specialisations if your type does not meet the assumptions above (e.g. for serialisation) (cpp file)
     // 6. Register your type and corresponding python type in AppPart.cpp
 
+    template <typename T>
+    inline GeometryDefaultExtension<T>::GeometryDefaultExtension(){ }
+
+    // Specialised constructors go here so that specialisation is before the template instantiation
+    // Specialised default constructors are inline, because a full specialisation otherwise shall go in the cpp file, but there it would be after the template instantiation.
+    template <>
+    inline GeometryDefaultExtension<long>::GeometryDefaultExtension():value(0){}
+
+    // instantiate the types so that other translation units (python wrappers) can access template
+    //constructors other than the default.
+    template class GeometryDefaultExtension<long>;
+    template class GeometryDefaultExtension<std::string>;
+
     // Prefer alias to typedef item 9
     using GeometryIntExtension = GeometryDefaultExtension<long>;
     using GeometryStringExtension = GeometryDefaultExtension<std::string>;
diff --git a/src/Mod/Part/App/GeometryIntExtensionPyImp.cpp b/src/Mod/Part/App/GeometryIntExtensionPyImp.cpp
index 872335ce3e..f05930ea1c 100644
--- a/src/Mod/Part/App/GeometryIntExtensionPyImp.cpp
+++ b/src/Mod/Part/App/GeometryIntExtensionPyImp.cpp
@@ -48,7 +48,7 @@ std::string GeometryIntExtensionPy::representation(void) const
 
 PyObject *GeometryIntExtensionPy::PyMake(struct _typeobject *, PyObject *, PyObject *)  // Python wrapper
 {
-    // create a new instance of PointPy and the Twin object
+    // create a new instance of the python object and the Twin object
     return new GeometryIntExtensionPy(new GeometryIntExtension);
 }
 
@@ -68,11 +68,18 @@ int GeometryIntExtensionPy::PyInit(PyObject* args, PyObject* /*kwd*/)
         return 0;
     }
 
-
+    PyErr_Clear();
+    char * pystr;
+    if (PyArg_ParseTuple(args, "ls", &Id,&pystr)) {
+        this->getGeometryIntExtensionPtr()->setValue(Id);
+        this->getGeometryIntExtensionPtr()->setName(pystr);
+        return 0;
+    }
 
     PyErr_SetString(PyExc_TypeError, "GeometryIntExtension constructor accepts:\n"
     "-- empty parameter list\n"
-    "-- long int\n");
+    "-- long int\n"
+    "-- long int, string\n");
     return -1;
 }
 
diff --git a/src/Mod/Part/App/GeometryStringExtensionPyImp.cpp b/src/Mod/Part/App/GeometryStringExtensionPyImp.cpp
index 3b4eb41d89..9cbd54df29 100644
--- a/src/Mod/Part/App/GeometryStringExtensionPyImp.cpp
+++ b/src/Mod/Part/App/GeometryStringExtensionPyImp.cpp
@@ -50,7 +50,7 @@ std::string GeometryStringExtensionPy::representation(void) const
 
 PyObject *GeometryStringExtensionPy::PyMake(struct _typeobject *, PyObject *, PyObject *)  // Python wrapper
 {
-    // create a new instance of PointPy and the Twin object
+    // create a new instance of the python object and the Twin object
     return new GeometryStringExtensionPy(new GeometryStringExtension);
 }
 
@@ -70,11 +70,19 @@ int GeometryStringExtensionPy::PyInit(PyObject* args, PyObject* /*kwd*/)
         return 0;
     }
 
+    PyErr_Clear();
+    char * pystr;
+    if (PyArg_ParseTuple(args, "ss", &pstr, &pystr)) {
+        this->getGeometryStringExtensionPtr()->setValue(pstr);
+        this->getGeometryStringExtensionPtr()->setName(pystr);
+        return 0;
+    }
 
 
     PyErr_SetString(PyExc_TypeError, "GeometryStringExtension constructor accepts:\n"
     "-- empty parameter list\n"
-    "-- string\n");
+    "-- string\n"
+    "-- string, string\n");
     return -1;
 }