README.md in uniqueness-1.0.0 vs README.md in uniqueness-1.1.0

@@ -49,9 +49,11 @@
     end
 
 You can customize the generated string by
 passing an options hash. The following keys are supported:
 
+`:trigger_on` when to be generated, can be one of ActiveRecord callbacks (`before_validation`, `before_create`, `before_save`, `after_initialize`), default to __:before_validation__
+
 `:length` number of characters, defaults to __32__
 
 `:type` type of string, can be one of: `:human`, `:auto`, defaults to __:auto__
 
 Human type generates strings easier to read by excluding ambiguous characters like `1, 5, 8, B, o, O, I, l, s, u`.