diff --git a/app/models/problem.rb b/app/models/problem.rb
--- a/app/models/problem.rb
+++ b/app/models/problem.rb
@@ -3,6 +3,7 @@
   belongs_to :description
   has_and_belongs_to_many :contests, :uniq => true
   has_many :test_pairs, :dependent => :delete_all
+  has_many :testcases, :dependent => :destroy
 
   validates_presence_of :name
   validates_format_of :name, :with => /^\w+$/