diff --git a/opm/input/eclipse/Utility/Functional.hpp b/opm/input/eclipse/Utility/Functional.hpp
index b3e044ae9..d5ab67141 100644
--- a/opm/input/eclipse/Utility/Functional.hpp
+++ b/opm/input/eclipse/Utility/Functional.hpp
@@ -24,6 +24,7 @@
 #include <iterator>
 #include <vector>
 #include <numeric>
+#include <functional>
 
 namespace Opm {