diff --git a/flake.nix b/flake.nix
index 2d3e12d..e3ca5fd 100644
--- a/flake.nix
+++ b/flake.nix
@@ -6,6 +6,7 @@
   ##############
 
   inputs = {
+    master.url = "github:nixos/nixpkgs";
     nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
     stable.url = "github:nixos/nixpkgs/nixos-21.11";
     nur.url = "github:nix-community/NUR";
diff --git a/overlays/default.nix b/overlays/default.nix
index 77b8c0d..83f8536 100644
--- a/overlays/default.nix
+++ b/overlays/default.nix
@@ -2,6 +2,11 @@
 
 final: prev: {
   python-dev = import ./python.nix final prev;
+  fish = final.master.fish;
+  master = import inputs.master {
+    inherit (prev) system;
+    config.allowUnfree = true;
+  };
   stable = import inputs.stable {
     inherit (prev) system;
     config.allowUnfree = true;