--- spack-src/src/example/pegtl/json_classes.hpp.org	2020-02-14 11:07:25.117102793 +0900
+++ spack-src/src/example/pegtl/json_classes.hpp	2020-02-14 11:08:06.841397607 +0900
@@ -35,9 +35,7 @@
       {
       }
 
-      ~json_base()
-      {
-      }
+      virtual ~json_base() = default;
    };
 
    inline std::ostream& operator<<( std::ostream& o, const json_base& j )