1 files changed, 1 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb b/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb
index 1fab50418a..1b7adc3f39 100644
--- a/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb
+++ b/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb
@@ -45,6 +45,7 @@ module ActiveRecord
           end
           options[:conditions] = conditions
           options[:joins] = @join_sql
+          options[:readonly] ||= false
 
           if options[:order] && @options[:order]
             options[:order] = "#{options[:order]}, #{@options[:order]}"