diff --git a/app/controllers/topics_controller.rb b/app/controllers/topics_controller.rb
index 002f2aa0103..6bc4fa406b7 100644
--- a/app/controllers/topics_controller.rb
+++ b/app/controllers/topics_controller.rb
@@ -503,7 +503,7 @@ class TopicsController < ApplicationController
     user = User.find_by(username: params[:username])
     guardian.ensure_can_remove_allowed_users!(topic, user)
 
-    if topic.remove_allowed_user(current_user, user)
+    if topic&.remove_allowed_user(current_user, user)
       render json: success_json
     else
       render json: failed_json, status: 422