diff --git a/include/openmc/mesh.h b/include/openmc/mesh.h
index 13138a739b..02bd3bc5a2 100644
--- a/include/openmc/mesh.h
+++ b/include/openmc/mesh.h
@@ -720,7 +720,7 @@ private:
   int get_bin_from_element(const libMesh::Elem* elem) const;
 
   // Data members
-  unique_ptr<libMesh::MeshBase> unique_m_; //!< pointer to the libMesh MeshBase instance, only used if mesh is created inside OpenMC
+  unique_ptr<libMesh::MeshBase> unique_m_ = nullptr; //!< pointer to the libMesh MeshBase instance, only used if mesh is created inside OpenMC
   libMesh::MeshBase* m_; //!< pointer to libMesh MeshBase instance, always set during intialization
   vector<unique_ptr<libMesh::PointLocatorBase>>
     pl_; //!< per-thread point locators
diff --git a/src/mesh.cpp b/src/mesh.cpp
index 8e9d4bcecc..dfa443b7f5 100644
--- a/src/mesh.cpp
+++ b/src/mesh.cpp
@@ -2324,6 +2324,7 @@ const std::string LibMesh::mesh_lib_type = "libmesh";
 
 LibMesh::LibMesh(pugi::xml_node node) : UnstructuredMesh(node)
 {
+  // filename_ and length_multiplier_ will already be set by the UnstructuredMesh constructor
   set_mesh_pointer_from_filename(filename_);
   set_length_multiplier(length_multiplier_);
   initialize();