diff --git a/app/assets/javascripts/discourse/app/mixins/open-composer.js b/app/assets/javascripts/discourse/app/mixins/open-composer.js
index 128bb838001..b96bc5ca638 100644
--- a/app/assets/javascripts/discourse/app/mixins/open-composer.js
+++ b/app/assets/javascripts/discourse/app/mixins/open-composer.js
@@ -7,11 +7,15 @@ export default Mixin.create({
   openComposer(controller) {
     let categoryId = controller.get("category.id");
 
-    if (
-      !controller.canCreateTopicOnCategory &&
-      this.siteSettings.default_subcategory_on_read_only_category
-    ) {
-      categoryId = controller.get("defaultSubcategory.id");
+    if (this.siteSettings.default_subcategory_on_read_only_category) {
+      if (
+        !controller.canCreateTopicOnCategory &&
+        controller.canCreateTopicOnSubCategory
+      ) {
+        categoryId = controller.get("defaultSubcategory.id");
+      } else {
+        categoryId = this.siteSettings.default_composer_category;
+      }
     }
 
     if (
diff --git a/app/assets/javascripts/discourse/app/routes/build-category-route.js b/app/assets/javascripts/discourse/app/routes/build-category-route.js
index 40bb36abee1..e29def7cc37 100644
--- a/app/assets/javascripts/discourse/app/routes/build-category-route.js
+++ b/app/assets/javascripts/discourse/app/routes/build-category-route.js
@@ -157,26 +157,24 @@ export default (filterArg, params) => {
 
       let canCreateTopicOnCategory =
         canCreateTopic && category.get("permission") === PermissionType.FULL;
-
+      let cannotCreateTopicOnCategory = !canCreateTopicOnCategory;
       let defaultSubcategory;
       let canCreateTopicOnSubCategory;
 
-      if (
-        !canCreateTopicOnCategory &&
-        this.siteSettings.default_subcategory_on_read_only_category
-      ) {
-        defaultSubcategory = category.subcategories.find((subcategory) => {
-          return subcategory.get("permission") === PermissionType.FULL;
-        });
+      if (this.siteSettings.default_subcategory_on_read_only_category) {
+        cannotCreateTopicOnCategory = false;
 
-        canCreateTopicOnSubCategory = !!defaultSubcategory;
+        if (!canCreateTopicOnCategory && category.subcategories) {
+          defaultSubcategory = category.subcategories.find((subcategory) => {
+            return subcategory.get("permission") === PermissionType.FULL;
+          });
+          canCreateTopicOnSubCategory = !!defaultSubcategory;
+        }
       }
 
       this.controllerFor("navigation/category").setProperties({
         canCreateTopicOnCategory,
-        cannotCreateTopicOnCategory: !(
-          canCreateTopicOnCategory || canCreateTopicOnSubCategory
-        ),
+        cannotCreateTopicOnCategory,
         canCreateTopic,
         canCreateTopicOnSubCategory,
         defaultSubcategory,
diff --git a/spec/fabricators/category_fabricator.rb b/spec/fabricators/category_fabricator.rb
index eb6dbcbd0cf..6932d40ffcc 100644
--- a/spec/fabricators/category_fabricator.rb
+++ b/spec/fabricators/category_fabricator.rb
@@ -8,7 +8,7 @@ end
 
 Fabricator(:category_with_definition, from: :category) { skip_category_definition false }
 
-Fabricator(:private_category, from: :category) do
+Fabricator(:category_with_group_and_permission, from: :category) do
   transient :group
   transient :permission_type
 
@@ -17,7 +17,6 @@ Fabricator(:private_category, from: :category) do
   user
 
   after_build do |cat, transients|
-    cat.update!(read_restricted: true)
     cat.category_groups.build(
       group_id: transients[:group].id,
       permission_type: transients[:permission_type] || CategoryGroup.permission_types[:full],
@@ -25,6 +24,10 @@ Fabricator(:private_category, from: :category) do
   end
 end
 
+Fabricator(:private_category, from: :category_with_group_and_permission) do
+  after_build { |cat, transients| cat.update!(read_restricted: true) }
+end
+
 Fabricator(:private_category_with_definition, from: :private_category) do
   skip_category_definition false
 end
diff --git a/spec/system/composer/default_to_subcategory_spec.rb b/spec/system/composer/default_to_subcategory_spec.rb
index 7de89c9fcd1..add412d8e83 100644
--- a/spec/system/composer/default_to_subcategory_spec.rb
+++ b/spec/system/composer/default_to_subcategory_spec.rb
@@ -6,32 +6,63 @@ describe "Default to Subcategory when parent Category doesn't allow posting",
   fab!(:user) { Fabricate(:user) }
   fab!(:group) { Fabricate(:group) }
   fab!(:group_user) { Fabricate(:group_user, user: user, group: group) }
+  fab!(:default_latest_category) { Fabricate(:category) }
   fab!(:category) { Fabricate(:private_category, group: group, permission_type: 3) }
   fab!(:subcategory) do
     Fabricate(:private_category, parent_category_id: category.id, group: group, permission_type: 1)
   end
+  fab!(:category_with_no_subcategory) do
+    Fabricate(:category_with_group_and_permission, group: group, permission_type: 3)
+  end
   let(:category_page) { PageObjects::Pages::Category.new }
-  before { sign_in(user) }
 
-  describe "Setting enabled and can't post on parent category" do
-    before { SiteSetting.default_subcategory_on_read_only_category = true }
-
-    it "should have 'New Topic' button enabled and default Subcategory set in the composer" do
-      category_page.visit(category)
-      expect(category_page).to have_button("New Topic", disabled: false)
-      category_page.new_topic_button.click
-      select_kit =
-        PageObjects::Components::SelectKit.new(page.find("#reply-control.open .category-chooser"))
-      expect(select_kit).to have_selected_value(subcategory.id)
+  describe "anon user" do
+    it "can visit the category" do
+      category_page.visit(category_with_no_subcategory)
+      select_kit = PageObjects::Components::SelectKit.new(page.find(".navigation-container"))
+      expect(select_kit).to have_selected_value(category_with_no_subcategory.id)
     end
   end
 
-  describe "Setting disabled and can't post on parent category" do
-    before { SiteSetting.default_subcategory_on_read_only_category = false }
+  describe "logged in user" do
+    before { sign_in(user) }
+    describe "default_subcategory_on_read_only_category setting enabled and can't post on parent category" do
+      before do
+        SiteSetting.default_subcategory_on_read_only_category = true
+        SiteSetting.default_composer_category = default_latest_category.id
+      end
+      describe "Category has subcategory" do
+        it "should have 'New Topic' button enabled and default Subcategory set in the composer" do
+          category_page.visit(category)
+          expect(category_page).to have_button("New Topic", disabled: false)
+          category_page.new_topic_button.click
+          select_kit =
+            PageObjects::Components::SelectKit.new(
+              page.find("#reply-control.open .category-chooser"),
+            )
+          expect(select_kit).to have_selected_value(subcategory.id)
+        end
+      end
+      describe "Category does not have subcategory" do
+        it "should have the 'New Topic' button enabled and default Subcategory set to latest default subcategory" do
+          category_page.visit(category_with_no_subcategory)
+          expect(category_page).to have_button("New Topic", disabled: false)
+          category_page.new_topic_button.click
+          select_kit =
+            PageObjects::Components::SelectKit.new(
+              page.find("#reply-control.open .category-chooser"),
+            )
+          expect(select_kit).to have_selected_value(default_latest_category.id)
+        end
+      end
+    end
 
-    it "should have 'New Topic' button disabled" do
-      category_page.visit(category)
-      expect(category_page).to have_button("New Topic", disabled: true)
+    describe "Setting disabled and can't post on parent category" do
+      before { SiteSetting.default_subcategory_on_read_only_category = false }
+      it "should have 'New Topic' button disabled" do
+        category_page.visit(category)
+        expect(category_page).to have_button("New Topic", disabled: true)
+      end
     end
   end
 end