diff --git a/lib/costs_project_patch.rb b/lib/costs_project_patch.rb
index 151aabbed3..f89729a122 100644
--- a/lib/costs_project_patch.rb
+++ b/lib/costs_project_patch.rb
@@ -8,7 +8,7 @@ module CostsProjectPatch
     base.class_eval do
       unloadable
       
-      has_many :cost_objects
+      has_many :cost_objects, :dependent => :destroy
       has_many :rates, :class_name => 'HourlyRate'
       
       has_many :member_groups, :class_name => 'Member',