diff --git a/ApplicationCode/ReservoirDataModel/RigCurveDataTools.h b/ApplicationCode/ReservoirDataModel/RigCurveDataTools.h
index deec6c889a..8633ad0a05 100644
--- a/ApplicationCode/ReservoirDataModel/RigCurveDataTools.h
+++ b/ApplicationCode/ReservoirDataModel/RigCurveDataTools.h
@@ -21,6 +21,7 @@
 
 #include "cvfAssert.h"
 
+#include <cstddef>
 #include <vector>