[Bug]: route serialize does not extract param off proxy

packages/@ember/-internals/routing/lib/system/route.ts

@@ -18,7 +18,7 @@ import {
   Object as EmberObject,
   typeOf,
 } from '@ember/-internals/runtime';
-import { lookupDescriptor } from '@ember/-internals/utils';
+import { isProxy, lookupDescriptor } from '@ember/-internals/utils';
 import Controller from '@ember/controller';
 import { assert, deprecate, info, isTesting } from '@ember/debug';
 import { ROUTER_EVENTS } from '@ember/deprecated-features';
@@ -63,6 +63,8 @@ export function defaultSerialize(
       object[name] = get(model, name);
     } else if (/_id$/.test(name)) {
       object[name] = get(model, 'id');
+    } else if (isProxy(model)) {
+      object[name] = get(model, name);
     }
   } else {
     object = getProperties(model, params);

packages/@ember/-internals/routing/tests/system/route_test.js

@@ -4,6 +4,7 @@ import Service, { inject as injectService } from '@ember/service';
 import { Object as EmberObject } from '@ember/-internals/runtime';
 import EmberRoute from '../../lib/system/route';
 import { defineProperty } from '../../../metal';
+import ObjectProxy from '@ember/-internals/runtime/lib/system/object_proxy';
 
 let route, routeOne, routeTwo, lookupHash;
 
@@ -280,6 +281,19 @@ moduleFor(
       assert.deepEqual(route.serialize(model, ['post_id']), { post_id: 3 }, 'serialized correctly');
     }
 
+    ['@test returns model.id if model is a Proxy'](assert) {
+      // `key` in target should fail
+      // let model = new Proxy({ id: 3 }, {
+      //   get(target, prop) { target[prop] },
+      //   has() {
+      //     return false;
+      //   }
+      // });
+      let model = ObjectProxy.create({ content: { id: 3 } });
+
+      assert.deepEqual(route.serialize(model, ['id']), { id: 3 }, 'serialized Proxy correctly');
+    }
+
     ['@test returns undefined if model is not set'](assert) {
       assert.equal(route.serialize(undefined, ['post_id']), undefined, 'serialized correctly');
     }