diff --git a/Framework/Catalog/inc/MantidCatalog/ONCatEntity.h b/Framework/Catalog/inc/MantidCatalog/ONCatEntity.h
index 6c48f214512ec2d65b75a4fa1405637660a57a96..2933598cf0342e24e098813b7ba60c838e4c4332 100644
--- a/Framework/Catalog/inc/MantidCatalog/ONCatEntity.h
+++ b/Framework/Catalog/inc/MantidCatalog/ONCatEntity.h
@@ -4,6 +4,7 @@
 #include "MantidCatalog/DllConfig.h"
 #include "MantidKernel/make_unique.h"
 
+#include <string>
 #include <vector>
 
 #include <boost/optional.hpp>