diff --git a/app/controllers/api/v2/notifications_controller.rb b/app/controllers/api/v2/notifications_controller.rb
index cc38b95114..848c361cfc 100644
--- a/app/controllers/api/v2/notifications_controller.rb
+++ b/app/controllers/api/v2/notifications_controller.rb
@@ -46,7 +46,7 @@ class Api::V2::NotificationsController < Api::BaseController
   end
 
   def show
-    @notification = current_account.notifications.without_suspended.find_by!(group_key: params[:group_key])
+    @notification = current_account.notifications.without_suspended.by_group_key(params[:group_key]).take!
     presenter = GroupedNotificationsPresenter.new(NotificationGroup.from_notifications([@notification]))
     render json: presenter, serializer: REST::DedupNotificationGroupSerializer
   end
@@ -57,7 +57,7 @@ class Api::V2::NotificationsController < Api::BaseController
   end
 
   def dismiss
-    current_account.notifications.where(group_key: params[:group_key]).destroy_all
+    current_account.notifications.by_group_key(params[:group_key]).destroy_all
     render_empty
   end
 
diff --git a/app/models/notification.rb b/app/models/notification.rb
index 695f39a316..b1f095901c 100644
--- a/app/models/notification.rb
+++ b/app/models/notification.rb
@@ -106,6 +106,7 @@ class Notification < ApplicationRecord
   validates :type, inclusion: { in: TYPES }
 
   scope :without_suspended, -> { joins(:from_account).merge(Account.without_suspended) }
+  scope :by_group_key, ->(group_key) { group_key&.start_with?('ungrouped-') ? where(id: group_key.delete_prefix('ungrouped-')) : where(group_key: group_key) }
 
   def type
     @type ||= (super || LEGACY_TYPE_CLASS_MAP[activity_type]).to_sym
diff --git a/spec/requests/api/v2/notifications_spec.rb b/spec/requests/api/v2/notifications_spec.rb
index b2f6d71b51..a7608e1419 100644
--- a/spec/requests/api/v2/notifications_spec.rb
+++ b/spec/requests/api/v2/notifications_spec.rb
@@ -365,6 +365,18 @@ RSpec.describe 'Notifications' do
         .to start_with('application/json')
     end
 
+    context 'with an ungrouped notification' do
+      let(:notification) { Fabricate(:notification, account: user.account, type: :favourite) }
+
+      it 'returns http success' do
+        get "/api/v2/notifications/ungrouped-#{notification.id}", headers: headers
+
+        expect(response).to have_http_status(200)
+        expect(response.content_type)
+          .to start_with('application/json')
+      end
+    end
+
     context 'when notification belongs to someone else' do
       let(:notification) { Fabricate(:notification, group_key: 'foobar') }
 
@@ -396,6 +408,19 @@ RSpec.describe 'Notifications' do
       expect { notification.reload }.to raise_error(ActiveRecord::RecordNotFound)
     end
 
+    context 'with an ungrouped notification' do
+      let(:notification) { Fabricate(:notification, account: user.account, type: :favourite) }
+
+      it 'destroys the notification' do
+        post "/api/v2/notifications/ungrouped-#{notification.id}/dismiss", headers: headers
+
+        expect(response).to have_http_status(200)
+        expect(response.content_type)
+          .to start_with('application/json')
+        expect { notification.reload }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+    end
+
     context 'when notification belongs to someone else' do
       let(:notification) { Fabricate(:notification, group_key: 'foobar') }