diff --git a/config/users/kat/gui/firefox-tst/default.nix b/config/users/kat/gui/firefox-tst/default.nix
deleted file mode 100644
index 84f3ee89..00000000
--- a/config/users/kat/gui/firefox-tst/default.nix
+++ /dev/null
@@ -1,19 +0,0 @@
-{ stdenv, sass, base16 }:
-
-stdenv.mkDerivation ({
-  pname = "firefox-tst-css";
-  version = "0.0.1";
-
-  phases = [ "buildPhase" ];
-
-  src = ./tst.sass;
-
-  buildInputs = [
-    sass
-  ];
-
-  buildPhase = ''
-    substituteAll $src firefox-tst-substituted.sass
-    sass firefox-tst-substituted.sass $out --sourcemap=none
-  '';
-} // base16)
diff --git a/config/users/kat/gui/firefox.nix b/config/users/kat/gui/firefox.nix
index b23793fa..1d333d8b 100644
--- a/config/users/kat/gui/firefox.nix
+++ b/config/users/kat/gui/firefox.nix
@@ -10,11 +10,9 @@ let
     "toolkit.legacyUserProfileCustomizations.stylesheets" = true;
     "svg.context-properties.content.enabled" = true;
   };
-  firefox-tst = pkgs.callPackage ./firefox-tst { base16 = config.kw.hexColors; };
 in
 {
-
-  home.file.".mozilla/tst.css".source = firefox-tst;
+  home.file.".mozilla/tst.css".source = pkgs.firefox-tst { base16 = config.kw.hexColors; };
 
   programs.zsh.shellAliases = {
     ff-pm = "firefox --ProfileManager";
diff --git a/overlays/default.nix b/overlays/default.nix
index 000ceefb..0dae2c27 100644
--- a/overlays/default.nix
+++ b/overlays/default.nix
@@ -1,30 +1,17 @@
 { sources, system ? builtins.currentSystem, ... }@args:
 
 let
-  overlay = self: super: {
-    nur = import sources.nur {
-      nurpkgs = self;
-      pkgs = self;
-    };
-    anicca = self.callPackage sources.anicca {};
-    rustfmt = super.rustfmt.overrideAttrs ({ patches ? [ ], ... }: {
-      patches = patches ++ [
-        # Adds an option variant that merges all use statements into a single block.
-        # Taken from https://github.com/rust-lang/rustfmt/pull/4680
-        ./Implement-One-option-for-imports_granularity-4669.patch
-      ];
-    });
-    linuxPackagesFor = kernel: (super.linuxPackagesFor kernel).extend (_: ksuper: {
-      zfsUnstable = ksuper.zfsUnstable.overrideAttrs (old: { meta = old.meta // { broken = false; }; });
-    });
-  };
   pkgs = import sources.nixpkgs {
     overlays = [
-      (import (sources.arcexprs + "/overlay.nix"))
-      (import (sources.katexprs + "/overlay.nix"))
+      (import ./nur { inherit sources; })
       (import sources.emacs-overlay)
-      overlay
-    ];
+      (import ./rustfmt)
+      (import ./firefox-tst)
+    ] ++ (map (path: import "${path}/overlay.nix") [
+      sources.arcexprs
+      sources.katexprs
+      sources.anicca
+    ]);
     config = {
       allowUnfree = true;
       permittedInsecurePackages = [
@@ -33,4 +20,4 @@ let
     };
   };
 in
-pkgs
+  pkgs
diff --git a/overlays/firefox-tst/default.nix b/overlays/firefox-tst/default.nix
new file mode 100644
index 00000000..29b87c03
--- /dev/null
+++ b/overlays/firefox-tst/default.nix
@@ -0,0 +1,21 @@
+final: prev: {
+  firefox-tst = final.callPackage ({ stdenv, sass }: { base16 }:
+
+  stdenv.mkDerivation ({
+    pname = "firefox-tst-css";
+    version = "0.0.1";
+
+    phases = [ "buildPhase" ];
+
+    src = ./tst.sass;
+
+    buildInputs = [
+      sass
+    ];
+
+    buildPhase = ''
+      substituteAll $src firefox-tst-substituted.sass
+      sass firefox-tst-substituted.sass $out --sourcemap=none --style expanded
+    '';
+  } // base16)) {};
+}
diff --git a/config/users/kat/gui/firefox-tst/tst.sass b/overlays/firefox-tst/tst.sass
similarity index 100%
rename from config/users/kat/gui/firefox-tst/tst.sass
rename to overlays/firefox-tst/tst.sass
diff --git a/overlays/nur/default.nix b/overlays/nur/default.nix
new file mode 100644
index 00000000..85f74cbb
--- /dev/null
+++ b/overlays/nur/default.nix
@@ -0,0 +1,6 @@
+{ sources }: final: prev: {
+  nur = import sources.nur {
+    nurpkgs = final;
+    pkgs = final;
+  };
+}
diff --git a/overlays/Implement-One-option-for-imports_granularity-4669.patch b/overlays/rustfmt/Implement-One-option-for-imports_granularity-4669.patch
similarity index 100%
rename from overlays/Implement-One-option-for-imports_granularity-4669.patch
rename to overlays/rustfmt/Implement-One-option-for-imports_granularity-4669.patch
diff --git a/overlays/rustfmt/default.nix b/overlays/rustfmt/default.nix
new file mode 100644
index 00000000..2a9d606a
--- /dev/null
+++ b/overlays/rustfmt/default.nix
@@ -0,0 +1,9 @@
+final: prev: {
+  rustfmt = prev.rustfmt.overrideAttrs ({ patches ? [ ], ... }: {
+    patches = patches ++ [
+      # Adds an option variant that merges all use statements into a single block.
+      # Taken from https://github.com/rust-lang/rustfmt/pull/4680
+      ./Implement-One-option-for-imports_granularity-4669.patch
+    ];
+  });
+}
diff --git a/overlays/zfsUnstable/default.nix b/overlays/zfsUnstable/default.nix
new file mode 100644
index 00000000..9c34a195
--- /dev/null
+++ b/overlays/zfsUnstable/default.nix
@@ -0,0 +1,5 @@
+final: prev: {
+    linuxPackagesFor = kernel: (final.linuxPackagesFor kernel).extend (_: kfinal: {
+      zfsUnstable = kfinal.zfsUnstable.overrideAttrs (old: { meta = old.meta // { broken = false; }; });
+    });
+}