diff --git a/src/MANYBODY/pair_polymorphic.h b/src/MANYBODY/pair_polymorphic.h
index 32f1c5414a..e7c3cd0d26 100644
--- a/src/MANYBODY/pair_polymorphic.h
+++ b/src/MANYBODY/pair_polymorphic.h
@@ -22,6 +22,7 @@ PairStyle(polymorphic,PairPolymorphic)
 
 #include "pair.h"
 #include <cmath>
+#include <cstring>
 
 namespace LAMMPS_NS {