How to fix EXTEND_PROTOTYPES deprecation ?

Just updated deps and got

DEPRECATION: Accessing Ember.EXTEND_PROTOTYPES is deprecated, please migrate to Ember.ENV.EXTEND_PROTOTYPES [deprecation id: ember-env.old-extend-prototypes]

Nothing can find about it

I have standard config in config/environment.js

   EmberENV: {
      FEATURES: {
        // Here you can enable experimental features on an ember canary build
        // e.g. 'with-controller': true
      },
      EXTEND_PROTOTYPES: {
        // Prevent Ember Data from overriding Date.parse.
        Date: false
      }
    },

[ro0gr]

So in my case it was an outdated transitive ember-inflector@2.2.0 dependency.

yarn upgrade ember-cli-mirage ember-data fixed the issue for me.

[ddoria921]

I ran into the same deprecation warning. I updated ember-inflector to "^2.3.0" in my package.json and then did a yarn install. After that the warning was gone.