diff --git a/app/controllers/topics_controller.rb b/app/controllers/topics_controller.rb
index 986266be..9f280d0b 100644
--- a/app/controllers/topics_controller.rb
+++ b/app/controllers/topics_controller.rb
@@ -20,7 +20,7 @@ class TopicsController < ApplicationController
       @topics = []
       @maps = []
     end
-    @all= @topics.concat(@maps).sort { |a, b| a.name <=> b.name }
+    @all= @topics.to_a.concat(@maps.to_a).sort { |a, b| a.name <=> b.name }
     
     render json: autocomplete_array_json(@all)
   end