diff --git a/build.sh b/build.sh
new file mode 100755
index 00000000..62c554c4
--- /dev/null
+++ b/build.sh
@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+set -euo pipefail
+set -x
+
+BUILD_ARGS=()
+
+if [ -d "../nixpkgs" -a -z "${NO_LOCAL:-}" ]
+then
+    BUILD_ARGS+=("--override-input" "nixpkgs" "../nixpkgs" "--no-write-lock-file")
+fi
+
+sudo nix build --profile /nix/var/nix/profiles/system ".#nixosConfigurations.$(hostname).config.system.build.toplevel" --no-link "${BUILD_ARGS[@]}" && \
+    sudo nix shell -vv /nix/var/nix/profiles/system -c switch-to-configuration switch
diff --git a/update.sh b/update.sh
index 41fe64cd..cdaf4d00 100755
--- a/update.sh
+++ b/update.sh
@@ -2,11 +2,8 @@
 set -euo pipefail
 set -x
 
-BUILD_ARGS=()
-
 if [ -d "../nixpkgs" -a -z "${NO_LOCAL:-}" ]
 then
-    BUILD_ARGS+=("--override-input" "nixpkgs" "../nixpkgs" "--no-write-lock-file")
     pushd ../nixpkgs
     git fetch --all --prune
     git rebase upstream/nixos-unstable-small || exit 1
@@ -16,5 +13,4 @@ fi
 
 nix flake update --update-input nixpkgs --update-input home-manager --update-input flake-utils
 
-sudo nix build --profile /nix/var/nix/profiles/system ".#nixosConfigurations.$(hostname).config.system.build.toplevel" --no-link "${BUILD_ARGS[@]}" && \
-    sudo nix --experimental-features "nix-command flakes" shell -vv /nix/var/nix/profiles/system -c switch-to-configuration switch
+./build.sh