Ember queryParams not updating URL

I'm trying to set queryParams in an Ember controller, but they don't seem to be updating the URL at all.

I have this abbreviated mixin being applied to the route:

import Ember from 'ember';
import ControllerPaginationMixin from './controller-pagination';

export default Ember.Mixin.create({
  setupController(controller, model) {
    this._super(controller, model);

    controller.reopen(ControllerPaginationMixin);
  }
});

And here's the abbreviated controller mixin that is applied above:

import Ember from 'ember';

export default Ember.Mixin.create({
  sortKey: null,
  queryParams: ['sortKey'],
  actions: {
    sort(key) {
      this.set('sortKey', key);
  }
});

When I call the sort method from a component, I can see in the Ember Inspector that the sortKey property has been changed to the correct new value, but the URL remains unchanged. Am I missing something?