diff --git a/src/algorithms/calorimetry/SimCalorimeterHitProcessor.cc b/src/algorithms/calorimetry/SimCalorimeterHitProcessor.cc
index 81c1745599..524f2d9593 100644
--- a/src/algorithms/calorimetry/SimCalorimeterHitProcessor.cc
+++ b/src/algorithms/calorimetry/SimCalorimeterHitProcessor.cc
@@ -20,10 +20,9 @@
 #include <functional>
 #include <gsl/pointers>
 #include <limits>
+#include <map>
 #include <stdexcept>
 #include <tuple>
-#include <unordered_map>
-#include <map>
 #include <variant>
 #include <vector>