pluralising root key when using arraySerializer

lib/active_model/serializer/array_serializer.rb

@@ -19,7 +19,7 @@ module ActiveModel
       end
 
       def json_key
-        @objects.first.json_key if @objects.first
+        @objects.first.json_key.pluralize if @objects.first
       end
 
       def root=(root)

lib/active_model/serializer/fieldset.rb

@@ -13,7 +13,7 @@ module ActiveModel
 
       def fields_for(serializer)
         key = serializer.json_key
-        fields[key.to_sym]
+        fields[key.to_sym] || fields[key.pluralize.to_sym]
       end
 
     private