diff --git a/app/models/budget/ballot.rb b/app/models/budget/ballot.rb
index bf7851883..9b9a089d6 100644
--- a/app/models/budget/ballot.rb
+++ b/app/models/budget/ballot.rb
@@ -11,12 +11,12 @@ class Budget
       investments.sum(:price).to_i
     end
 
-    def amount_spent(heading)
-      investments.by_heading(heading).sum(:price).to_i
+    def amount_spent(heading_id)
+      investments.by_heading(heading_id).sum(:price).to_i
     end
 
     def amount_available(heading)
-      budget.heading_price(heading) - amount_spent(heading)
+      budget.heading_price(heading) - amount_spent(heading.try(:id))
     end
   end
 end