pbkdf2 docs
diff --git a/docs/hazmat/primitives/index.rst b/docs/hazmat/primitives/index.rst
index b115fdb..2a29bd8 100644
--- a/docs/hazmat/primitives/index.rst
+++ b/docs/hazmat/primitives/index.rst
@@ -9,6 +9,7 @@
     cryptographic-hashes
     hmac
     symmetric-encryption
+    key-derivation-functions
     padding
     constant-time
     interfaces