diff --git a/src/posts/rss-gen.org b/src/posts/rss-gen.org
index cc80cf7..f599262 100644
--- a/src/posts/rss-gen.org
+++ b/src/posts/rss-gen.org
@@ -224,7 +224,7 @@ For example my script uses =date= from GNU coreutils and not the =BSD= date
 from my OS, which makes the script more portable.
 This also take care of using the URI perl package.
 
-Along my script I have a =shell.nix= file containing:
+Along my script I have a [[file:rss-gen/shell.nix][=shell.nix=]] file containing:
 
 #+begin_src nix
 # { pkgs ? import <nixpkgs> {} }:
diff --git a/src/posts/rss-gen/shell.nix b/src/posts/rss-gen/shell.nix
new file mode 100644
index 0000000..67e388e
--- /dev/null
+++ b/src/posts/rss-gen/shell.nix
@@ -0,0 +1,5 @@
+# { pkgs ? import <nixpkgs> {} }:
+{ pkgs ? import (fetchTarball https://github.com/NixOS/nixpkgs/archive/19.09-beta.tar.gz) {} }:
+  pkgs.mkShell {
+    buildInputs = [ pkgs.coreutils pkgs.html-xml-utils pkgs.zsh ];
+  }