diff --git a/config.org b/config.org
index dddf733..99dd362 100644
--- a/config.org
+++ b/config.org
@@ -19,6 +19,8 @@
     - [[#enable-proc-macro-support][Enable proc macro support]]
   - [[#cc][C/C++]]
     - [[#default-style][Default style]]
+  - [[#nix][Nix]]
+    - [[#formatting][Formatting]]
 - [[#org-mode][Org mode]]
   - [[#directory][Directory]]
   - [[#appearance][Appearance]]
@@ -247,6 +249,16 @@ Setup the default format for C/C++ editing.
   (setq c-basic-offset 2))
 #+END_SRC
 
+** Nix
+
+*** Formatting
+
+Use [[https://github.com/kamadorueda/alejandra][alejandra]] to format Nix code.
+
+#+begin_src emacs-lisp
+(set-formatter! 'alejandra "alejandra --quiet" :modes '(nix-mode))
+#+end_src
+
 * Org mode
 
 ** Directory
diff --git a/init.el b/init.el
index e14c646..c0a94d5 100644
--- a/init.el
+++ b/init.el
@@ -55,7 +55,7 @@
        (evil +everywhere); come to the dark side, we have cookies
        ;;file-templates    ; auto-snippets for empty files
        fold              ; (nigh) universal code folding
-       ;;(format +onsave)  ; automated prettiness
+       (format)  ; automated prettiness
        ;;god               ; run Emacs commands without modifier keys
        ;;lispy             ; vim for lisp, for people who don't like vim
        ;;multiple-cursors  ; editing in many places at once