Problem with dynamic prop on `$subscribe`

VueJS
1

Problem with dynamic prop on $subscribe, when I change it many times

data() {
            return {
                param: '',
                posts:[]
         };
},
meteor: {
            $subscribe: {
                postsPub(){
                    return [this.param];
               }
            },
            posts(){
                return Posts.find().fetch();
            },
        },
methods:{
   handleParamChange(){
       // change param.......
   }
}