diff --git a/src/celeritas/phys/PrimaryGeneratorOptions.hh b/src/celeritas/phys/PrimaryGeneratorOptions.hh
index 76a8ced6f5..aa7504157f 100644
--- a/src/celeritas/phys/PrimaryGeneratorOptions.hh
+++ b/src/celeritas/phys/PrimaryGeneratorOptions.hh
@@ -9,6 +9,7 @@
 
 #include <functional>
 #include <random>
+#include <algorithm>
 
 #include "corecel/io/StringEnumMapper.hh"
 #include "geocel/Types.hh"