diff --git a/lib/serialisation/XmlIO.h b/lib/serialisation/XmlIO.h
index eaa8174b..792505d4 100644
--- a/lib/serialisation/XmlIO.h
+++ b/lib/serialisation/XmlIO.h
@@ -103,7 +103,8 @@ namespace Grid
   {
     std::ostringstream os;
     
-    os << std::boolalpha << x;
+    os.precision(16);
+    os << std::scientific << std::boolalpha << x;
     pugi::xml_node leaf = node_.append_child(s.c_str());
     leaf.append_child(pugi::node_pcdata).set_value(os.str().c_str());
   }