diff --git a/src/simsopt/field/magneticfieldclasses.py b/src/simsopt/field/magneticfieldclasses.py
index 286d436fa..474217b2b 100644
--- a/src/simsopt/field/magneticfieldclasses.py
+++ b/src/simsopt/field/magneticfieldclasses.py
@@ -489,6 +489,7 @@ def __init__(self, field, degree, rrange, phirange, zrange, extrapolate=True, nf
             logger.warning(fr"Sure about phirange[1]={phirange[1]}? When exploiting rotational symmetry, the interpolant is never evaluated for phi>2\pi/nfp.")
 
         sopp.InterpolatedField.__init__(self, field, degree, rrange, phirange, zrange, extrapolate, nfp, stellsym)
+        self.__field == field
 
     def to_vtk(self, filename, h=0.1):
         """Export the field evaluated on a regular grid for visualisation with e.g. Paraview."""
diff --git a/src/simsoptpp/py_shared_ptr.h b/src/simsoptpp/py_shared_ptr.h
deleted file mode 100644
index be7ecce99..000000000
--- a/src/simsoptpp/py_shared_ptr.h
+++ /dev/null
@@ -1,30 +0,0 @@
-#pragma once
-
-// see https://github.com/pybind/pybind11/issues/1389
-
-#include <pybind11/pybind11.h>
-#include <memory>
-namespace py = pybind11;
-
-template <typename T> class py_shared_ptr {
-    private:
-        std::shared_ptr<T> _impl;
-
-    public:
-        using element_type = T;
-
-        py_shared_ptr(T *ptr) {
-            py::object pyobj = py::cast(ptr);
-            PyObject* pyptr = pyobj.ptr();
-            Py_INCREF(pyptr);
-            std::shared_ptr<PyObject> vec_py_ptr(
-                    pyptr, [](PyObject *ob) { Py_DECREF(ob); });
-            _impl = std::shared_ptr<T>(vec_py_ptr, ptr);
-        }
-
-        py_shared_ptr(std::shared_ptr<T> r): _impl(r){}
-
-        operator std::shared_ptr<T>() { return _impl; }
-
-        T* get() const {return _impl.get();}
-};
diff --git a/src/simsoptpp/python.cpp b/src/simsoptpp/python.cpp
index 48e1977aa..f556ba541 100644
--- a/src/simsoptpp/python.cpp
+++ b/src/simsoptpp/python.cpp
@@ -1,8 +1,6 @@
 #include "pybind11/pybind11.h"
 #include "pybind11/stl.h"
 #include "pybind11/functional.h"
-#include "py_shared_ptr.h"
-PYBIND11_DECLARE_HOLDER_TYPE(T, py_shared_ptr<T>);
 #define FORCE_IMPORT_ARRAY
 #include "xtensor-python/pyarray.hpp"     // Numpy bindings
 typedef xt::pyarray<double> PyArray;
diff --git a/src/simsoptpp/python_curves.cpp b/src/simsoptpp/python_curves.cpp
index 70e73e8b8..41d29bb12 100644
--- a/src/simsoptpp/python_curves.cpp
+++ b/src/simsoptpp/python_curves.cpp
@@ -2,8 +2,6 @@
 #include "pybind11/stl.h"
 #include "xtensor-python/pyarray.hpp"     // Numpy bindings
 typedef xt::pyarray<double> PyArray;
-#include "py_shared_ptr.h"
-PYBIND11_DECLARE_HOLDER_TYPE(T, py_shared_ptr<T>);
 using std::shared_ptr;
 
 
@@ -90,16 +88,16 @@ template <typename T, typename S> void register_common_curve_methods(S &c) {
 }
 
 void init_curves(py::module_ &m) {
-    auto pycurve = py::class_<PyCurve, py_shared_ptr<PyCurve>, PyCurveTrampoline<PyCurve>>(m, "Curve")
+    auto pycurve = py::class_<PyCurve, shared_ptr<PyCurve>, PyCurveTrampoline<PyCurve>>(m, "Curve")
         .def(py::init<vector<double>>());
     register_common_curve_methods<PyCurve>(pycurve);
 
-    auto pycurvexyzfourier = py::class_<PyCurveXYZFourier, py_shared_ptr<PyCurveXYZFourier>, PyCurveXYZFourierTrampoline<PyCurveXYZFourier>, PyCurve>(m, "CurveXYZFourier")
+    auto pycurvexyzfourier = py::class_<PyCurveXYZFourier, shared_ptr<PyCurveXYZFourier>, PyCurveXYZFourierTrampoline<PyCurveXYZFourier>, PyCurve>(m, "CurveXYZFourier")
         .def(py::init<vector<double>, int>())
         .def_readonly("dofs", &PyCurveXYZFourier::dofs);
     register_common_curve_methods<PyCurveXYZFourier>(pycurvexyzfourier);
 
-    auto pycurverzfourier = py::class_<PyCurveRZFourier, py_shared_ptr<PyCurveRZFourier>, PyCurveRZFourierTrampoline<PyCurveRZFourier>, PyCurve>(m, "CurveRZFourier")
+    auto pycurverzfourier = py::class_<PyCurveRZFourier, shared_ptr<PyCurveRZFourier>, PyCurveRZFourierTrampoline<PyCurveRZFourier>, PyCurve>(m, "CurveRZFourier")
         //.def(py::init<int, int>())
         .def(py::init<vector<double>, int, int, bool>())
         .def_readwrite("rc", &PyCurveRZFourier::rc)
diff --git a/src/simsoptpp/python_surfaces.cpp b/src/simsoptpp/python_surfaces.cpp
index 606c9f628..0d19bd6fa 100644
--- a/src/simsoptpp/python_surfaces.cpp
+++ b/src/simsoptpp/python_surfaces.cpp
@@ -2,8 +2,6 @@
 #include "pybind11/stl.h"
 #include "xtensor-python/pyarray.hpp"     // Numpy bindings
 typedef xt::pyarray<double> PyArray;
-#include "py_shared_ptr.h"
-PYBIND11_DECLARE_HOLDER_TYPE(T, py_shared_ptr<T>);
 using std::shared_ptr;
 using std::vector;