Vuejs: update Map prop value for child component

I have an array and a map in the parent components.
By using a button, I update the value of both of them.
I expected both value will be updated automatically once the prop value changed, but only the array was being updated.
How can I listen to the update of the Map in the child components?

// Parent Component
<template>
  <div>   
    <ChildComponent :map-data.sync="mapData" :array-data.sync="arrayData"></ChildComponent>
    <br>
    <b-button variant="outline-primary" v-on:click.prevent="updateData">update data</b-button>
  </div>

</template>

<script>
  export default {
    name: "Parent-Component",
    components: {
      ChildComponent
    },
    data() {
      return {
        mapData: new Map(),
        arrayData: []
      }
    },
    created() {
      this.mapData.set("A", 0);
    },
    methods: {
      updateData() {
        this.mapData.set("A", this.mapData.get("A") + 1);
        this.arrayData.push("newData");
      }
    }
  };
</script>


// Child component script
<script>
  export default {
    name: "Child-Component",
    props:['arrayData', 'mapData'],
    components: {
    },
    watch: {
      mapData: function () {
        console.log("this is never called");
      },
      arrayData: function() {
        console.log("this is called as expected");
      }
    }
  };
</script>