diff --git a/include/openmc/distribution.h b/include/openmc/distribution.h
index 2e210b7abb..b7d0e47210 100644
--- a/include/openmc/distribution.h
+++ b/include/openmc/distribution.h
@@ -37,13 +37,15 @@ UPtrDist distribution_from_xml(pugi::xml_node node);
 
 class DiscreteIndex {
 public:
-  explicit Discrete(pugi::xml_node node);
-  Discrete(const double* p, int n);
+  explicit DiscreteIndex(pugi::xml_node node);
+  DiscreteIndex(const double* p, int n);
+
+  void assign(const double* p, int n);
 
   //! Sample a value from the distribution
   //! \param seed Pseudorandom number seed pointer
   //! \return Sampled value
-  size_t sample(uint64_t* seed) const override;
+  size_t sample(uint64_t* seed) const;
 
   // Properties
   const vector<double>& prob() const { return prob_; }
@@ -81,9 +83,9 @@ public:
   const vector<size_t>& alias() const { return di_->alias(); }
 
 private:
-  vector<double> x_;             //!< Possible outcomes
-  unique_ptr<DiscreteIndex> di_; //!< discrete probability distribution of
-                                 //!< outcome indices
+  vector<double> x_; //!< Possible outcomes
+  DiscreteIndex di_; //!< discrete probability distribution of
+                     //!< outcome indices
 };
 
 //==============================================================================
diff --git a/include/openmc/distribution_spatial.h b/include/openmc/distribution_spatial.h
index 9ca9c0684b..9fba950602 100644
--- a/include/openmc/distribution_spatial.h
+++ b/include/openmc/distribution_spatial.h
@@ -114,8 +114,8 @@ public:
 
 private:
   int32_t mesh_idx_ {C_NONE};
-  unique_ptr<DiscreteIndex> elem_idx_dist_; //!< Distribution of
-                                            //!< mesh element indices
+  DiscreteIndex elem_idx_dist_; //!< Distribution of
+                                //!< mesh element indices
 };
 
 //==============================================================================
diff --git a/src/distribution.cpp b/src/distribution.cpp
index 2066e5a8c1..18fa414490 100644
--- a/src/distribution.cpp
+++ b/src/distribution.cpp
@@ -25,8 +25,9 @@ namespace openmc {
 DiscreteIndex::DiscreteIndex(pugi::xml_node node)
 {
   auto params = get_node_array<double>(node, "parameters");
+  std::size_t n = params.size() / 2;
 
-  prob_.assign(params.begin(), params.end());
+  prob_.assign(params.begin() + n, params.end());
 
   this->init_alias();
 }
@@ -38,6 +39,13 @@ DiscreteIndex::DiscreteIndex(const double* p, int n)
   this->init_alias();
 }
 
+void DiscreteIndex::assign(const double* p, int n)
+{
+  prob_.assign(p, p + n);
+
+  this->init_alias();
+}
+
 void DiscreteIndex::init_alias()
 {
   normalize();
@@ -111,21 +119,19 @@ void DiscreteIndex::normalize()
 // Discrete implementation
 //==============================================================================
 
-Discrete::Discrete(pugi::xml_node node)
+Discrete::Discrete(pugi::xml_node node) : di_(node)
 {
   auto params = get_node_array<double>(node, "parameters");
 
   std::size_t n = params.size() / 2;
 
   x_.assign(params.begin(), params.begin() + n);
-  di_ = new DiscreteIndex(params.begin() + n, n)
 }
 
-Discrete::Discrete(const double* x, const double* p, int n)
+Discrete::Discrete(const double* x, const double* p, int n) : di_(p, n)
 {
 
   x_.assign(x, x + n);
-  di_ = new DiscreteIndex(params.begin() + n, n)
 }
 
 double Discrete::sample(uint64_t* seed) const
diff --git a/src/distribution_spatial.cpp b/src/distribution_spatial.cpp
index c2d370b17a..694617ac5b 100644
--- a/src/distribution_spatial.cpp
+++ b/src/distribution_spatial.cpp
@@ -231,7 +231,7 @@ MeshSpatial::MeshSpatial(pugi::xml_node node)
     }
   }
 
-  elem_idx_dist_ = make_unique<DiscreteIndex>(strengths.data(), n_bins);
+  elem_idx_dist_.assign(strengths.data(), n_bins);
 }
 
 Position MeshSpatial::sample(uint64_t* seed) const