diff --git a/README.md b/README.md
index fce8f30..01059bf 100644
--- a/README.md
+++ b/README.md
@@ -132,6 +132,7 @@ You can define the following configuration options globally or on the CaptchaTyp
 * **as_url**: if set to true, a URL will be used in the image tag and will handle captcha generation. This can be used in a multiple-server environment and support IE6/7 (default=false)
 * **invalid_message**: error message displayed when an non-matching code is submitted (default="Bad code value")
 * **bypass_code**: code that will always validate the captcha (default=null)
+* **valid_keys**: names that are able to be used for a captcha form type (default=[captcha])
 
 Example :
 
@@ -166,6 +167,11 @@ This will use the bundle's route of "/generate-captcha/{key}" to handle the gene
         resource: "@GregwarCaptchaBundle/Resources/config/routing/routing.yml"
         prefix: /_gcb
 
+If you are using multiple captchas or assigning names other than the default "captcha", you will need to whitelist your captcha names in the "valid_keys" configuration:
+
+    gregwar_captcha:
+        valid_keys: [registration_captcha, confirmation_captcha]
+
 Form Theming
 ============