diff --git a/README.md b/README.md
index f687a20..00cc2bd 100644
--- a/README.md
+++ b/README.md
@@ -101,6 +101,7 @@ You can define the following type option :
 * **height**: the height of the captcha image (default=40)
 * **length**: the length of the captcha (number of chars, default 5)
 * **charset**: the charset used for code generation (default=abcdefhjkmnprstuvwxyz23456789)
+* **keep_value**: the value will be the same until the form is posted, even if the page is refreshed (default=true)
 * **as_file**: if set to true an image file will be created instead of embedding to please IE6/7 (default=false)
 * **image_folder**: name of folder for captcha images relative to public web folder in case **as_file** ist set to true (default="captcha")
 * **web_path**: absolute path to public web folder (default="%kernel.root_dir%/../web")