diff --git a/docs/primitives/symmetric-encryption.rst b/docs/primitives/symmetric-encryption.rst
index c4f78a7..be86229 100644
--- a/docs/primitives/symmetric-encryption.rst
+++ b/docs/primitives/symmetric-encryption.rst
@@ -79,6 +79,19 @@
                         of the cipher.  Reuse of a ``nonce`` with a given
                         ``key`` can allow recovery of the original plaintext.
 
+.. class:: cryptography.primitives.block.modes.CFB(initialization_vector)
+
+    CFB (Cipher Feedback) is a mode of operation for block ciphers. It
+    transforms a block cipher into a stream cipher.
+
+    :param bytes initialization_vector: Must be random bytes. They do not need
+                                        to be kept secret (they can be included
+                                        in a transmitted message). Must be the
+                                        same number of bytes as the
+                                        ``block_size`` of the cipher. Do not
+                                        reuse an ``initialization_vector`` with
+                                        a given ``key``.
+
 
 Insecure Modes
 --------------