diff --git a/src/geometry.cpp b/src/geometry.cpp
index 22e3cbfe34..2c83e38366 100644
--- a/src/geometry.cpp
+++ b/src/geometry.cpp
@@ -108,33 +108,31 @@ find_cell(Particle* p, int search_surf) {
 
       // Find the distribcell instance number.
       if (c.material_.size() > 1 || c.sqrtkT_.size() > 1) {
-        //TODO: off-by-one indexing
-        int distribcell_index = c.distribcell_index_ - 1;
         int offset = 0;
         for (int i = 0; i < p->n_coord; i++) {
           Cell& c_i {*cells[p->coord[i].cell]};
           if (c_i.type_ == FILL_UNIVERSE) {
-            offset += c_i.offset_[distribcell_index];
+            offset += c_i.offset_[c.distribcell_index_];
           } else if (c_i.type_ == FILL_LATTICE) {
             Lattice& lat {*lattices[p->coord[i+1].lattice-1]};
             int i_xyz[3] {p->coord[i+1].lattice_x,
                           p->coord[i+1].lattice_y,
                           p->coord[i+1].lattice_z};
             if (lat.are_valid_indices(i_xyz)) {
-              offset += lat.offset(distribcell_index, i_xyz);
+              offset += lat.offset(c.distribcell_index_, i_xyz);
             }
           }
         }
-        p->cell_instance = offset + 1;
+        p->cell_instance = offset;
       } else {
-        p->cell_instance = 1;
+        p->cell_instance = 0;
       }
 
       // Set the material and temperature.
       p->last_material = p->material;
       int32_t mat;
       if (c.material_.size() > 1) {
-        mat = c.material_[p->cell_instance-1];
+        mat = c.material_[p->cell_instance];
       } else {
         mat = c.material_[0];
       }
@@ -145,7 +143,7 @@ find_cell(Particle* p, int search_surf) {
       }
       p->last_sqrtkT = p->sqrtkT;
       if (c.sqrtkT_.size() > 1) {
-        p->sqrtkT = c.sqrtkT_[p->cell_instance-1];
+        p->sqrtkT = c.sqrtkT_[p->cell_instance];
       } else {
         p->sqrtkT = c.sqrtkT_[0];
       }
diff --git a/src/geometry_aux.cpp b/src/geometry_aux.cpp
index 9c1d17b4d6..a304790125 100644
--- a/src/geometry_aux.cpp
+++ b/src/geometry_aux.cpp
@@ -220,8 +220,7 @@ prepare_distribcell(int32_t* filter_cell_list, int n)
 
   // Search through universes for distributed cells and assign each one a
   // unique distribcell array index.
-  //TODO: off-by-one
-  int distribcell_index = 1;
+  int distribcell_index = 0;
   std::vector<int32_t> target_univ_ids;
   for (Universe* u : universes) {
     for (auto cell_indx : u->cells_) {
diff --git a/src/tallies/tally_filter_distribcell.F90 b/src/tallies/tally_filter_distribcell.F90
index ae4e09023d..f35ffc3ec4 100644
--- a/src/tallies/tally_filter_distribcell.F90
+++ b/src/tallies/tally_filter_distribcell.F90
@@ -59,14 +59,14 @@ contains
       do i = 1, p % n_coord
         if (cells(p % coord(i) % cell + 1) % type() == FILL_UNIVERSE) then
           offset = offset + cells(p % coord(i) % cell + 1) &
-               % offset(distribcell_index-1)
+               % offset(distribcell_index)
         elseif (cells(p % coord(i) % cell + 1) % type() == FILL_LATTICE) then
           if (lattices(p % coord(i + 1) % lattice) % are_valid_indices([&
                p % coord(i + 1) % lattice_x, &
                p % coord(i + 1) % lattice_y, &
                p % coord(i + 1) % lattice_z])) then
             offset = offset + lattices(p % coord(i + 1) % lattice) &
-                 % offset(distribcell_index - 1, &
+                 % offset(distribcell_index, &
                  [p % coord(i + 1) % lattice_x, &
                  p % coord(i + 1) % lattice_y, &
                  p % coord(i + 1) % lattice_z])
@@ -155,10 +155,10 @@ contains
     ! Get the distribcell index for this cell
     map = cells(i_cell) % distribcell_index()
 
-    path_len = distribcell_path_len(i_cell-1, map-1, target_offset, &
+    path_len = distribcell_path_len(i_cell-1, map, target_offset, &
                                     root_universe)
     allocate(path_c(path_len))
-    call distribcell_path(i_cell-1, map-1, target_offset, root_universe, &
+    call distribcell_path(i_cell-1, map, target_offset, root_universe, &
                           path_c)
     do i = 1, min(path_len, MAX_LINE_LEN)
       if (path_c(i) == C_NULL_CHAR) exit