diff --git a/README.markdown b/README.markdown
index 2d933fa..09466b1 100644
--- a/README.markdown
+++ b/README.markdown
@@ -323,7 +323,7 @@ After copying and pasting code to do this several times I decided to package it
 
 DatabaseCleaner comes with safeguards against:
 
-* Running in production (checking for `ENV`, `RACK_ENV`, and `RAILS_ENV`)
+* Running in production (checking for `ENV`, `APP_ENV`, `RACK_ENV`, and `RAILS_ENV`)
 * Running against a remote database (checking for a `DATABASE_URL` that does not include `localhost`, `.local` or `127.0.0.1`)
 
 Both safeguards can be disabled separately as follows.