Document the other consequence of losing your key
diff --git a/docs/fernet.rst b/docs/fernet.rst
index 241bf1e..3f0cdde 100644
--- a/docs/fernet.rst
+++ b/docs/fernet.rst
@@ -30,7 +30,9 @@
Generates a fresh fernet key. Keep this some place safe! If you lose it
you'll no longer be able to decrypt messages; if anyone else gains
- access to it, they'll be able to decrypt all of your messages.
+ access to it, they'll be able to decrypt all of your messages, and
+ they'll also be able forge arbitrary messages which will be
+ authenticated and decrypted.
.. method:: encrypt(plaintext)