diff --git a/src/opm/parser/eclipse/EclipseState/Grid/Operate.cpp b/src/opm/parser/eclipse/EclipseState/Grid/Operate.cpp
index d57ab2969..3aceb7dce 100644
--- a/src/opm/parser/eclipse/EclipseState/Grid/Operate.cpp
+++ b/src/opm/parser/eclipse/EclipseState/Grid/Operate.cpp
@@ -17,6 +17,7 @@
 */
 #include <cmath>
 #include <map>
+#include <string>
 
 #include "Operate.hpp"