diff --git a/default.nix b/default.nix
index 205076c..cd03f14 100644
--- a/default.nix
+++ b/default.nix
@@ -6,7 +6,13 @@
 # commands such as:
 #     nix-build -A mypackage
 
-{ pkgs ? import <nixpkgs> { } }:
+{
+  system ? builtins.currentSystem,
+  sources ? import ./sources.nix,
+  pkgs ? import sources.nixpkgs {
+    inherit system;
+  },
+}:
 
 {
   # The `lib`, `modules`, and `overlays` names are special
diff --git a/sources.nix b/sources.nix
new file mode 100644
index 0000000..765056e
--- /dev/null
+++ b/sources.nix
@@ -0,0 +1,12 @@
+# Read sources from flake.lock
+let
+  lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+
+  fetchSource =
+    args:
+    builtins.fetchTarball {
+      url = "https://github.com/${args.owner}/${args.repo}/archive/${args.rev}.tar.gz";
+      sha256 = args.narHash;
+    };
+in
+builtins.mapAttrs (name: value: fetchSource value.locked) lock.nodes