lib/mongoid/contextual/aggregable/mongo.rb in mongoid-9.0.0 vs lib/mongoid/contextual/aggregable/mongo.rb in mongoid-9.0.1

@@ -94,14 +94,17 @@
         #   aggregable.sum(:likes)
         #
         # @example Get the sum for the provided block.
         #   aggregable.sum(&:likes)
         #
-        # @param [ Symbol ] field The field to sum.
+        # @param [ Symbol | Numeric ] field The field to sum, or the initial
+        #    value of the sum when a block is given.
         #
         # @return [ Float ] The sum value.
         def sum(field = nil)
-          block_given? ? super() : aggregates(field)["sum"] || 0
+          return super(field || 0) if block_given?
+
+          aggregates(field)["sum"] || 0
         end
 
         private
 
         # Get the aggregation pipeline for provided field.