Setting an array of objects to sessionStorage

Ok, so I have this JSON:

{"Status":"OK!","ListaPermessi":
[{"IdPermesso":10,"Nome":"WIND_PARAMS"},
 {"IdPermesso":11,"Nome":"ADMIN_SERVER"},
 {"IdPermesso":21,"Nome":"REC"},
 {"IdPermesso":22,"Nome":"REC_DIST"},
 {"IdPermesso":23,"Nome":"REC_DIST_CR"}
]}

My code is:

var parsedResult = JSON.parse(result); // where result is the above JSON
if (parsedResult.Status === "OK!") {
    // Set sessionStorage vars
    if (typeof(Storage) !== "undefined") {
        // localStorage & sessionStorage support!

        sessionStorage.setItem("ListaPermessi", parsedResult.ListaPermessi);
    }
    else {
        // Sorry! No web storage support :(
    }
}

But... this is not working properly! After the assignment, the sessionStorage seen from Firebug looks like this:

sessionStorage:

• ListaPermessi = "[object Object],[object Object],[object Object],[object Object],[object Object]"

What is the proper way to assign an array of objects to a sessionStorage variable from javascript?