diff --git a/src/particle_data.cpp b/src/particle_data.cpp
index 8f4db5a8a9..7f1f9f4564 100644
--- a/src/particle_data.cpp
+++ b/src/particle_data.cpp
@@ -3,6 +3,7 @@
 #include "openmc/geometry.h"
 #include "openmc/nuclide.h"
 #include "openmc/photon.h"
+#include "openmc/settings.h"
 #include "openmc/tallies/derivative.h"
 #include "openmc/tallies/filter.h"
 #include "openmc/tallies/tally.h"
@@ -18,8 +19,10 @@ ParticleData::ParticleData()
 
   zero_delayed_bank();
 
-  // Every particle starts with no accumulated flux derivative.
-  if (!model::active_tallies.empty()) {
+  // Every particle starts with no accumulated flux derivative.  Note that in
+  // event mode, we construct the particle once up front, so have to run this
+  // even if the current batch is inactive.
+  if (!model::active_tallies.empty() || settings::event_based) {
     flux_derivs_.resize(model::tally_derivs.size());
     zero_flux_derivs();
   }