diff --git a/include/openmc/geometry_aux.h b/include/openmc/geometry_aux.h
index 28b19e315..899326a53 100644
--- a/include/openmc/geometry_aux.h
+++ b/include/openmc/geometry_aux.h
@@ -7,6 +7,7 @@
 #include <cstdint>
 #include <string>
 #include <unordered_map>
+#include <vector>
 
 #include "openmc/vector.h"
 
@@ -63,9 +64,12 @@ int32_t find_root_universe();
 
 //==============================================================================
 //! Populate all data structures needed for distribcells.
+//! \param user_distribcells A set of cell indices to create distribcell data
+//!   structures for regardless of whether or not they are part of a tally
+//!   filter.
 //==============================================================================
 
-void prepare_distribcell();
+void prepare_distribcell(const std::vector<int32_t>* user_distribcells = nullptr);
 
 //==============================================================================
 //! Recursively search through the geometry and count cell instances.
diff --git a/include/openmc/tallies/filter_cell_instance.h b/include/openmc/tallies/filter_cell_instance.h
index 789a4151e..387f7e591 100644
--- a/include/openmc/tallies/filter_cell_instance.h
+++ b/include/openmc/tallies/filter_cell_instance.h
@@ -44,6 +44,8 @@ public:
 
   const vector<CellInstance>& cell_instances() const { return cell_instances_; }
 
+  const std::unordered_set<int32_t>& cells() const { return cells_; }
+
   void set_cell_instances(gsl::span<CellInstance> instances);
 
 private:
diff --git a/src/geometry_aux.cpp b/src/geometry_aux.cpp
index 9d3062901..857803421 100644
--- a/src/geometry_aux.cpp
+++ b/src/geometry_aux.cpp
@@ -311,12 +311,18 @@ find_root_universe()
 //==============================================================================
 
 void
-prepare_distribcell()
+prepare_distribcell(const std::vector<int32_t>* user_distribcells)
 {
   write_message("Preparing distributed cell instances...", 5);
 
-  // Find all cells listed in a DistribcellFilter or CellInstanceFilter
   std::unordered_set<int32_t> distribcells;
+
+  // start with any cells manually specified via the C++ API
+  if (user_distribcells) {
+    distribcells.insert(user_distribcells->begin(), user_distribcells->end());
+  }
+
+  // Find all cells listed in a DistribcellFilter or CellInstanceFilter
   for (auto& filt : model::tally_filters) {
     auto* distrib_filt = dynamic_cast<DistribcellFilter*>(filt.get());
     auto* cell_inst_filt = dynamic_cast<CellInstanceFilter*>(filt.get());
@@ -324,7 +330,8 @@ prepare_distribcell()
       distribcells.insert(distrib_filt->cell());
     }
     if (cell_inst_filt) {
-      for (const auto& c_inst : cell_inst_filt->cell_instances()) distribcells.insert(c_inst.index_cell);
+      const auto& filter_cells = cell_inst_filt->cells();
+      distribcells.insert(filter_cells.begin(), filter_cells.end());
     }
   }