Spree Promo Multiple Automatic Promotions Bug

spree_promo.rb

# In spree/promo/lib/spree_promo.rb
             next if current_promotions.present? && !promotion.combine?
             amount = promotion.calculator.compute(self).abs
             amount = item_total if amount > item_total
-            if amount > 0
+            if amount > 0 && !promotion_credit_exists?(promotion)
               self.promotion_credits.create(
                   :source => promotion,
                   :amount => -amount,