lib/mongoid/contextual/aggregable/mongo.rb in mongoid-3.0.17 vs lib/mongoid/contextual/aggregable/mongo.rb in mongoid-3.0.18

@@ -102,10 +102,10 @@
         #
         # @return [ Float ] The sum value.
         #
         # @since 3.0.0
         def sum(field = nil)
-          block_given? ? super() : aggregates(field)["sum"]
+          block_given? ? super() : aggregates(field)["sum"] || 0
         end
 
         private
 
         # Get the finalize function.