diff --git a/include/Helmholtz.h b/include/Helmholtz.h
index 0f7a7845..613b8d76 100644
--- a/include/Helmholtz.h
+++ b/include/Helmholtz.h
@@ -2,6 +2,7 @@
 #ifndef HELMHOLTZ_H
 #define HELMHOLTZ_H
 
+#include <array>
 #include <vector>
 #include "rapidjson_include.h"
 //#include "Eigen/Core"