diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index 5179fa2188..de57725af2 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -277,7 +277,7 @@ module ActiveRecord
 
     def apply_modules(modules)
       unless modules.empty?
-        @extensions.concat modules
+        @extensions += modules
         modules.each {|extension| extend(extension) }
       end
     end