diff --git a/activemodel/lib/active_model/validations/validates.rb b/activemodel/lib/active_model/validations/validates.rb
index 43d9f82d9f..e28e7e9219 100644
--- a/activemodel/lib/active_model/validations/validates.rb
+++ b/activemodel/lib/active_model/validations/validates.rb
@@ -154,7 +154,7 @@ module ActiveModel
       # When creating custom validators, it might be useful to be able to specify
       # additional default keys. This can be done by overwriting this method.
       def _validates_default_keys
-        [:if, :unless, :on, :allow_blank, :allow_nil , :strict]
+        [:if, :unless, :on, :allow_blank, :allow_nil, :strict]
       end
 
       def _parse_validates_options(options)