diff --git a/libpympb/pympb.cpp b/libpympb/pympb.cpp
index 6e4a00240..2c3885199 100644
--- a/libpympb/pympb.cpp
+++ b/libpympb/pympb.cpp
@@ -676,7 +676,7 @@ void mode_solver::init(int p, bool reset_fields, geometric_object_list *geometry
                        meep_geom::material_data *_default_material) {
   int have_old_fields = 0;
 
-  default_material = _default_material;
+  set_default_material(_default_material);
 
   n[0] = grid_size.x;
   n[1] = grid_size.y;
@@ -909,7 +909,9 @@ void mode_solver::reset_epsilon(geometric_object_list *geometry) {
   };
 
   if (!epsilon_input_file.empty()) {
-    default_material = meep_geom::make_file_material(epsilon_input_file.c_str());
+    meep_geom::material_type material = meep_geom::make_file_material(epsilon_input_file.c_str());
+    set_default_material(material);
+    material_free(material);
   }
 
   // TODO: support mu_input_file
diff --git a/src/meepgeom.cpp b/src/meepgeom.cpp
index c96c8f879..eb7648395 100644
--- a/src/meepgeom.cpp
+++ b/src/meepgeom.cpp
@@ -29,7 +29,7 @@ namespace meep_geom {
 material_data vacuum_material_data;
 material_type vacuum = &vacuum_material_data;
 
-static void set_default_material(material_type _default_material) {
+void set_default_material(material_type _default_material) {
   if (default_material != NULL) {
     if (default_material == _default_material) return;
     material_free((material_type)default_material);
diff --git a/src/meepgeom.hpp b/src/meepgeom.hpp
index bb2f0d132..5802807e7 100644
--- a/src/meepgeom.hpp
+++ b/src/meepgeom.hpp
@@ -253,6 +253,7 @@ material_type make_material_grid(bool do_averaging, double beta, double eta, dou
 vector3 vec_to_vector3(const meep::vec &pt);
 meep::vec vector3_to_vec(const vector3 v3);
 
+void set_default_material(material_type _default_material);
 void epsilon_material_grid(material_data *md, double u);
 void epsilon_file_material(material_data *md, vector3 p);
 bool susceptibility_equal(const susceptibility &s1, const susceptibility &s2);