Optimizer trace does not escape double quotes, produces invalid JSON

SET optimizer_trace= 'enabled=on';

SELECT LENGTH("a");

SELECT json_valid(trace), trace FROM information_schema.optimizer_trace;

json_valid(trace)	trace

0	{

  "steps": [

    {

      "join_preparation": {

        "select_id": 1,

        "steps": [

          {

            "expanded_query": "select octet_length('a') AS `LENGTH("a")`"

          }

        ]

      }

    },

    {

      "join_optimization": {

        "select_id": 1,

        "steps": []

      }

    },

    {

      "join_execution": {

        "select_id": 1,

        "steps": []

      }

    }

  ]

}