diff --git a/docs/default.nix b/docs/default.nix
index 25c5b72..fdacce0 100644
--- a/docs/default.nix
+++ b/docs/default.nix
@@ -9,6 +9,8 @@ let
   # derivations.
   setupModule = {
     _module.args.pkgs = pkgs.lib.mkForce (nmd.scrubDerivations "pkgs" pkgs);
+
+    system.stateVersion = "19.09";
   };
 
   modules = import ../modules/module-list.nix {