diff --git a/app/assets/javascripts/darkswarm/directives/on_hand.js.coffee b/app/assets/javascripts/darkswarm/directives/on_hand.js.coffee
index 0173196138..1086363676 100644
--- a/app/assets/javascripts/darkswarm/directives/on_hand.js.coffee
+++ b/app/assets/javascripts/darkswarm/directives/on_hand.js.coffee
@@ -13,9 +13,7 @@ Darkswarm.directive "ofnOnHand", ->
       ngModel.$setDirty = setDirty
 
     ngModel.$parsers.push (viewValue) ->
-      on_hand = parseInt(attr.ofnOnHand)
-      finalized_quantity = parseInt(attr.finalizedquantity)
-      available_quantity = on_hand + finalized_quantity
+      available_quantity = scope.available_quantity()
       if parseInt(viewValue) > available_quantity
         alert t("js.insufficient_stock", {on_hand: available_quantity})
         viewValue = available_quantity
@@ -23,3 +21,8 @@ Darkswarm.directive "ofnOnHand", ->
         ngModel.$render()
 
       viewValue
+
+    scope.available_quantity = ->
+      on_hand = parseInt(attr.ofnOnHand)
+      finalized_quantity = parseInt(attr.finalizedquantity) || 0 # finalizedquantity is optional
+      on_hand + finalized_quantity