diff --git a/app/assets/javascripts/discourse/models/category.js.es6 b/app/assets/javascripts/discourse/models/category.js.es6
index e2683306183..0307766619f 100644
--- a/app/assets/javascripts/discourse/models/category.js.es6
+++ b/app/assets/javascripts/discourse/models/category.js.es6
@@ -257,7 +257,7 @@ Category.reopenClass({
     return Discourse.Site.currentProp("sortedCategories");
   },
 
-  idMap() {
+  _idMap() {
     return Discourse.Site.currentProp("categoriesById");
   },
 
@@ -273,7 +273,7 @@ Category.reopenClass({
     if (!id) {
       return;
     }
-    return Category.idMap()[id];
+    return Category._idMap()[id];
   },
 
   findByIds(ids = []) {
diff --git a/app/assets/javascripts/discourse/models/topic-tracking-state.js.es6 b/app/assets/javascripts/discourse/models/topic-tracking-state.js.es6
index a47a9341704..7db08a8fbee 100644
--- a/app/assets/javascripts/discourse/models/topic-tracking-state.js.es6
+++ b/app/assets/javascripts/discourse/models/topic-tracking-state.js.es6
@@ -410,12 +410,11 @@ const TopicTrackingState = EmberObject.extend({
 
   loadStates(data) {
     const states = this.states;
-    const idMap = Category.idMap();
 
     // I am taking some shortcuts here to avoid 500 gets for a large list
     if (data) {
       data.forEach(topic => {
-        var category = idMap[topic.category_id];
+        let category = Category.findById(topic.category_id);
         if (category && category.parent_category_id) {
           topic.parent_category_id = category.parent_category_id;
         }
diff --git a/test/javascripts/models/category-test.js.es6 b/test/javascripts/models/category-test.js.es6
index 58a0af8b3f3..9863eea36a0 100644
--- a/test/javascripts/models/category-test.js.es6
+++ b/test/javascripts/models/category-test.js.es6
@@ -184,19 +184,6 @@ QUnit.test("findSingleBySlug", assert => {
   );
 });
 
-QUnit.test("findByIds", assert => {
-  const store = createStore();
-  const categories = {
-    1: store.createRecord("category", { id: 1 }),
-    2: store.createRecord("category", { id: 2 })
-  };
-
-  sandbox.stub(Category, "idMap").returns(categories);
-  assert.deepEqual(Category.findByIds([1, 2, 3]), _.values(categories));
-
-  assert.deepEqual(Category.findByIds(), []);
-});
-
 QUnit.test("search with category name", assert => {
   const store = createStore(),
     category1 = store.createRecord("category", {