Use backend as keyword argument everywhere.
diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index e7d019d..76f68a1 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -37,7 +37,7 @@
.. doctest::
>>> from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
- >>> cipher = Cipher(algorithms.AES(key), modes.CBC(iv), backend)
+ >>> cipher = Cipher(algorithms.AES(key), modes.CBC(iv), backend=backend)
>>> encryptor = cipher.encryptor()
>>> ct = encryptor.update(b"a secret message") + encryptor.finalize()
>>> decryptor = cipher.decryptor()
@@ -179,7 +179,7 @@
>>> from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
>>> algorithm = algorithms.ARC4(key)
- >>> cipher = Cipher(algorithm, mode=None)
+ >>> cipher = Cipher(algorithm, mode=None, backend=backend)
>>> encryptor = cipher.encryptor()
>>> ct = encryptor.update(b"a secret message")
>>> decryptor = cipher.decryptor()