diff --git a/docs/fernet.rst b/docs/fernet.rst
index d44e737..3348889 100644
--- a/docs/fernet.rst
+++ b/docs/fernet.rst
@@ -6,7 +6,7 @@
 .. testsetup::
 
     import binascii
-    key = binascii.unhexlify(b"0" * 32)
+    key = binascii.unhexlify(b"0" * 64)
 
 
 `Fernet`_ is an implementation of symmetric (also known as "secret key")