diff --git a/bob/cli.py b/bob/cli.py
index ca6cec8..7945b1d 100644
--- a/bob/cli.py
+++ b/bob/cli.py
@@ -10,7 +10,7 @@ Options:
     --overwrite  allow overwriting of deployed archives.
 
 Configuration:
-    Environment Variables: AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_BUCKET
+    Environment Variables: AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, S3_BUCKET, S3_PREFIX (optional)
 """
 import os
 
@@ -71,4 +71,4 @@ def dispatch():
     try:
         main()
     except KeyboardInterrupt:
-        print 'ool.'
\ No newline at end of file
+        print 'ool.'