diff --git a/include/openmc/mesh.h b/include/openmc/mesh.h
index c15e25697..fbc6c46f5 100644
--- a/include/openmc/mesh.h
+++ b/include/openmc/mesh.h
@@ -666,9 +666,8 @@ class UnstructuredMesh : public Mesh {
 
 public:
   // Constructors
-  UnstructuredMesh() {};
+  UnstructuredMesh() { n_dimension_ = 3; };
   UnstructuredMesh(pugi::xml_node node);
-  UnstructuredMesh(const std::string& filename);
 
   static const std::string mesh_type;
   virtual std::string get_mesh_type() const override;
diff --git a/src/mesh.cpp b/src/mesh.cpp
index 3e4ff1a3e..b7396a25a 100644
--- a/src/mesh.cpp
+++ b/src/mesh.cpp
@@ -590,6 +590,8 @@ Position StructuredMesh::sample_element(
 
 UnstructuredMesh::UnstructuredMesh(pugi::xml_node node) : Mesh(node)
 {
+  n_dimension_ = 3;
+
   // check the mesh type
   if (check_for_node(node, "type")) {
     auto temp = get_node_value(node, "type", true, true);
@@ -2519,7 +2521,9 @@ MOABMesh::MOABMesh(pugi::xml_node node) : UnstructuredMesh(node)
 }
 
 MOABMesh::MOABMesh(const std::string& filename, double length_multiplier)
+  : UnstructuredMesh()
 {
+  n_dimension_ = 3;
   filename_ = filename;
   set_length_multiplier(length_multiplier);
   initialize();
@@ -3242,6 +3246,7 @@ LibMesh::LibMesh(libMesh::MeshBase& input_mesh, double length_multiplier)
 LibMesh::LibMesh(const std::string& filename, double length_multiplier)
   : adaptive_(false)
 {
+  n_dimension_ = 3;
   set_mesh_pointer_from_filename(filename);
   set_length_multiplier(length_multiplier);
   initialize();