diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index 2f39017..ef6f087 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -12,9 +12,6 @@
     key = binascii.unhexlify(b"0" * 32)
     iv = binascii.unhexlify(b"0" * 32)
 
-    from cryptography.hazmat.bindings import default_backend
-    backend = default_backend()
-
 
 Symmetric encryption is a way to encrypt (hide the plaintext value) material
 where the sender and receiver both use the same key. Note that symmetric
@@ -37,6 +34,8 @@
     .. doctest::
 
         >>> from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
+        >>> from cryptography.hazmat.bindings import default_backend
+        >>> backend = default_backend()
         >>> cipher = Cipher(algorithms.AES(key), modes.CBC(iv), backend=backend)
         >>> encryptor = cipher.encryptor()
         >>> ct = encryptor.update(b"a secret message") + encryptor.finalize()
@@ -230,8 +229,9 @@
     .. doctest::
 
         >>> from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
+        >>> from cryptography.hazmat.bindings import default_backend
         >>> algorithm = algorithms.ARC4(key)
-        >>> cipher = Cipher(algorithm, mode=None, backend=backend)
+        >>> cipher = Cipher(algorithm, mode=None, backend=default_backend())
         >>> encryptor = cipher.encryptor()
         >>> ct = encryptor.update(b"a secret message")
         >>> decryptor = cipher.decryptor()
@@ -356,7 +356,8 @@
     .. doctest::
 
         >>> from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
-        >>> cipher = Cipher(algorithms.AES(key), modes.GCM(iv), backend)
+        >>> from cryptography.hazmat.bindings import default_backend
+        >>> cipher = Cipher(algorithms.AES(key), modes.GCM(iv), backend=default_backend())
         >>> encryptor = cipher.encryptor()
         >>> encryptor.authenticate_additional_data(b"authenticated but not encrypted payload")
         >>> ct = encryptor.update(b"a secret message") + encryptor.finalize()