diff --git a/lib/rocket_pants/rspec_matchers.rb b/lib/rocket_pants/rspec_matchers.rb
index cb2ae1a..41c32e4 100644
--- a/lib/rocket_pants/rspec_matchers.rb
+++ b/lib/rocket_pants/rspec_matchers.rb
@@ -21,6 +21,7 @@ def self.normalise_urls(object)
 
     # Converts it to JSON and back again.
     def self.normalise_as_json(object, options = {})
+      options = RocketPants.default_serializer_options.reverse_merge(options)
       options = options.reverse_merge(:compact => true) if object.is_a?(Array)
       object = RocketPants::Respondable.normalise_object(object, options)
       j = ActiveSupport::JSON