diff --git a/app/models/submission.rb b/app/models/submission.rb
--- a/app/models/submission.rb
+++ b/app/models/submission.rb
@@ -107,6 +107,8 @@
       errors.add_to_base("must specify problem")
     elsif !problem.available
       errors.add_to_base("must specify valid problem")
+    else
+      self.problem = problem
     end
   end