diff --git a/default.nix b/default.nix
index 56eb23c1..df93fc02 100644
--- a/default.nix
+++ b/default.nix
@@ -5,9 +5,8 @@
 # the root to be `default.nix`
 { }:
 let
-  mkPkgs = args: (import ./pkgs/additional/nixpkgs args).appendOverlays [
-    (import ./overlays/all.nix)
-  ];
+  mkPkgs = args: (import ./pkgs/additional/nixpkgs args).extend
+    (import ./overlays/all.nix);
   inherit (mkPkgs {}) lib;
 
   evalHost = { name, system, branch ? "master", variant ? null }:
diff --git a/pkgs/additional/mobile-nixos/default.nix b/pkgs/additional/mobile-nixos/default.nix
index cda92d06..6aaa753b 100644
--- a/pkgs/additional/mobile-nixos/default.nix
+++ b/pkgs/additional/mobile-nixos/default.nix
@@ -12,7 +12,7 @@ let
     hash = "sha256-MiVokKlpcJmfoGuWAMeW1En7gZ5hk0rCQArYm6P9XCc=";
   };
   overlay = import "${src}/overlay/overlay.nix";
-  final = pkgs.appendOverlays [ overlay ];
+  final = pkgs.extend overlay;
 in src.overrideAttrs (base: {
   # passthru only mobile-nixos' own packages -- not the whole nixpkgs-with-mobile-nixos-as-overlay:
   passthru = base.passthru // (overlay final pkgs);
diff --git a/pkgs/additional/nixpkgs-wayland/default.nix b/pkgs/additional/nixpkgs-wayland/default.nix
index b928a2a1..c6b0a239 100644
--- a/pkgs/additional/nixpkgs-wayland/default.nix
+++ b/pkgs/additional/nixpkgs-wayland/default.nix
@@ -21,7 +21,7 @@ let
   };
   overlay = evaluated.overlay;
 
-  final = pkgs.appendOverlays [ overlay ];
+  final = pkgs.extend overlay;
 in src.overrideAttrs (base: {
   # attributes required by update scripts
   pname = "nixpkgs-wayland";
diff --git a/pkgs/additional/sops-nix/default.nix b/pkgs/additional/sops-nix/default.nix
index a6e8e465..0db58267 100644
--- a/pkgs/additional/sops-nix/default.nix
+++ b/pkgs/additional/sops-nix/default.nix
@@ -16,7 +16,7 @@ let
     nixpkgs-stable = pkgs;  #< shameless lie :)
   };
   overlay = evaluated.overlays.default;
-  final = pkgs.appendOverlays [ overlay ];
+  final = pkgs.extend overlay;
 in src.overrideAttrs (base: {
   # attributes required by update scripts
   pname = "sops-nix";
diff --git a/pkgs/default.nix b/pkgs/default.nix
index 9031d551..d96e47a1 100644
--- a/pkgs/default.nix
+++ b/pkgs/default.nix
@@ -14,7 +14,7 @@ let
     inherit (py-final) callPackage;
     inherit pkgs;
   };
-  final' = if final != null then final else pkgs.appendOverlays [(_: _: sane-overlay)];
+  final' = if final != null then final else pkgs.extend (_: _: sane-overlay);
   sane-additional = with final'; {
     sane-data = import ../modules/data { inherit lib sane-lib; };
     sane-lib = import ../modules/lib final';