diff --git a/lib/squib/constants.rb b/lib/squib/constants.rb
index 9ed0dc4..ded0be5 100644
--- a/lib/squib/constants.rb
+++ b/lib/squib/constants.rb
@@ -95,6 +95,8 @@ module Squib
       'best' => 'subpixel',
       'good' => 'gray',
       'fast' => 'gray',
+      'gray' => 'gray',
+      'subpixel' => 'subpixel'
     }
     # These are parameters that are intended to be "expanded" across
     # range if they are singletons.