diff --git a/src/geometry.cpp b/src/geometry.cpp
index 3c7799c27d..f9aea182e7 100644
--- a/src/geometry.cpp
+++ b/src/geometry.cpp
@@ -127,11 +127,11 @@ find_cell_inner(Particle* p, const NeighborList* neighbor_list)
       if (c.material_.size() > 1 || c.sqrtkT_.size() > 1) {
         int offset = 0;
         for (int i = 0; i < p->n_coord_; i++) {
-          Cell& c_i {*model::cells[p->coord_[i].cell]};
+          const auto& c_i {*model::cells[p->coord_[i].cell]};
           if (c_i.type_ == FILL_UNIVERSE) {
             offset += c_i.offset_[c.distribcell_index_];
           } else if (c_i.type_ == FILL_LATTICE) {
-            Lattice& lat {*model::lattices[p->coord_[i+1].lattice-1]};
+            auto& lat {*model::lattices[p->coord_[i+1].lattice]};
             int i_xyz[3] {p->coord_[i+1].lattice_x,
                           p->coord_[i+1].lattice_y,
                           p->coord_[i+1].lattice_z};
@@ -227,7 +227,7 @@ find_cell_inner(Particle* p, const NeighborList* neighbor_list)
       p->coord_[p->n_coord_].uvw[2] = u.z;
 
       // Set lattice indices.
-      p->coord_[p->n_coord_].lattice = c.fill_ + 1;
+      p->coord_[p->n_coord_].lattice = c.fill_;
       p->coord_[p->n_coord_].lattice_x = i_xyz[0];
       p->coord_[p->n_coord_].lattice_y = i_xyz[1];
       p->coord_[p->n_coord_].lattice_z = i_xyz[2];
@@ -304,7 +304,7 @@ find_cell(Particle* p, bool use_neighbor_lists)
 extern "C" void
 cross_lattice(Particle* p, int lattice_translation[3])
 {
-  Lattice& lat {*model::lattices[p->coord_[p->n_coord_-1].lattice-1]};
+  auto& lat {*model::lattices[p->coord_[p->n_coord_-1].lattice]};
 
   if (settings::verbosity >= 10 || simulation::trace) {
     std::stringstream msg;
@@ -387,8 +387,8 @@ distance_to_boundary(Particle* p, double* dist, int* surface_crossed,
     level_surf_cross = surface_distance.second;
 
     // Find the distance to the next lattice tile crossing.
-    if (p->coord_[i].lattice != F90_NONE) {
-      Lattice& lat {*model::lattices[p->coord_[i].lattice-1]};
+    if (p->coord_[i].lattice != C_NONE) {
+      auto& lat {*model::lattices[p->coord_[i].lattice]};
       std::array<int, 3> i_xyz {p->coord_[i].lattice_x, p->coord_[i].lattice_y,
                                 p->coord_[i].lattice_z};
       //TODO: refactor so both lattice use the same position argument (which
diff --git a/src/output.cpp b/src/output.cpp
index 24e438b21c..8d41a98899 100644
--- a/src/output.cpp
+++ b/src/output.cpp
@@ -174,7 +174,7 @@ extern "C" void print_particle(Particle* p)
       std::cout << "    Universe         = " << u.id_ << "\n";
     }
 
-    if (p->coord_[i].lattice != F90_NONE) {
+    if (p->coord_[i].lattice != C_NONE) {
       const Lattice& lat {*model::lattices[p->coord_[i].lattice]};
       std::cout << "    Lattice          = " << lat.id_ << "\n";
       std::cout << "    Lattice position = (" << p->coord_[i].lattice_x
diff --git a/src/particle.cpp b/src/particle.cpp
index 287fef5766..059d4ac41a 100644
--- a/src/particle.cpp
+++ b/src/particle.cpp
@@ -37,7 +37,7 @@ LocalCoord::reset()
 {
   cell = C_NONE;
   universe = C_NONE;
-  lattice = 0;
+  lattice = C_NONE;
   lattice_x = 0;
   lattice_y = 0;
   rotated = false;
diff --git a/src/tallies/filter_distribcell.cpp b/src/tallies/filter_distribcell.cpp
index ce176cea3c..94f23621b1 100644
--- a/src/tallies/filter_distribcell.cpp
+++ b/src/tallies/filter_distribcell.cpp
@@ -45,7 +45,7 @@ DistribcellFilter::get_all_bins(const Particle* p, int estimator,
     if (c.type_ == FILL_UNIVERSE) {
       offset += c.offset_[distribcell_index];
     } else if (c.type_ == FILL_LATTICE) {
-      auto& lat {*model::lattices[p->coord_[i+1].lattice-1]};
+      auto& lat {*model::lattices[p->coord_[i+1].lattice]};
       int i_xyz[3] {p->coord_[i+1].lattice_x,
                     p->coord_[i+1].lattice_y,
                     p->coord_[i+1].lattice_z};