Hashtable as object literal serialization toJSON

No matter how hard i try i just cant get my hashtable serialized with JSONUtilities...

 //Atributes
 @SerializeField
 private var Attributes = new Hashtable({
     "strength"     : 1,
     "agility"    : 1,
     "mana"         : 1,
     "health"    : 1
 });

After serializing object that contains it i got no errors, just there is not a trace of it in output. Im sure that it can be serialized, i guess there is just something wrong in my understanding of the subject.

If someone can point me in right direction i would be grateful.