diff --git a/pkgs/web-greeter.nix b/pkgs/web-greeter.nix
index 427bff6..96f6d33 100644
--- a/pkgs/web-greeter.nix
+++ b/pkgs/web-greeter.nix
@@ -28,4 +28,5 @@ stdenv.mkDerivation {
     make install
   '';
   DESTDIR = placeholder "out";
+  PREFIX = "/";
 }