diff --git a/include/openmc/particle.h b/include/openmc/particle.h
index 134ebc105..00d37162b 100644
--- a/include/openmc/particle.h
+++ b/include/openmc/particle.h
@@ -329,7 +329,7 @@ public:
 
   std::vector<std::vector<Position>> tracks_;
 
-  NuBank nu_bank_[10];
+  NuBank nu_bank_[15];
 };
 
 } // namespace openmc
diff --git a/src/physics.cpp b/src/physics.cpp
index 8d0af575c..132c45bc9 100644
--- a/src/physics.cpp
+++ b/src/physics.cpp
@@ -169,6 +169,8 @@ create_fission_sites(Particle* p, int i_nuclide, const Reaction* rx,
   // First, if our bank is full then don't continue
   if (nu == 0) return;
 
+  assert( nu < 15 );
+
   // Initialize the counter of delayed neutrons encountered for each delayed
   // group.
   double nu_d[MAX_DELAYED_GROUPS] = {0.};