diff --git a/flake.nix b/flake.nix
index e76a5d9..2deec5e 100644
--- a/flake.nix
+++ b/flake.nix
@@ -61,18 +61,19 @@
         name = "e11sync-static";
         src = self;
         nativeBuildInputs = buildDeps;
-        buildPhase = ''
-          mkdir -p $out/static
-          export E11SYNC_STATIC_ROOT=$out/static
+        buildPhase = with pkgs; ''
+          mkdir -p static
+          export E11SYNC_STATIC_ROOT=static
           export E11SYNC_DEBUG=
           export E11SYNC_COMPRESS_OFFLINE=1
-          ${pkgs.python3}/bin/python3 ${self}/app/manage.py collectstatic
-          ${pkgs.python3}/bin/python3 ${self}/app/manage.py compress
+          ${python3}/bin/python3 ${self}/app/manage.py collectstatic
+          ${python3}/bin/python3 ${self}/app/manage.py compress
 
-          ${pkgs.findutils}/bin/find $out/static/CACHE -name '*.css' | \
-              ${pkgs.findutils}/bin/xargs -P8 -I{} sh -c \
-                  "${pkgs.zopfli}/bin/zopfli {} && ${pkgs.brotli}/bin/brotli {}"
+          ${findutils}/bin/find static/CACHE -name '*.css' | \
+              ${findutils}/bin/xargs -P''$(${coreutils}/bin/nproc) -I{} sh -c \
+                  "${zopfli}/bin/zopfli {} && ${brotli}/bin/brotli {}"
         '';
+        installPhase = ''mv static $out'';
       };
       packages.e11sync-gunicorn = pkgs.stdenv.mkDerivation {
         name = "e11sync-gunicorn";