diff --git a/nixos/hosts/ingress-proxy/default.nix b/nixos/hosts/ingress-proxy/default.nix
index 6e203d1..204be29 100644
--- a/nixos/hosts/ingress-proxy/default.nix
+++ b/nixos/hosts/ingress-proxy/default.nix
@@ -39,7 +39,7 @@ in {
 
         root = pkgs.stdenvNoCC.mkDerivation {
           name = name';
-          src = if src then src else builtins.fetchGit { inherit url rev; };
+          src = if src != null then src else builtins.fetchGit { inherit url rev; };
           installPhase = "cp -r $src $out";
         };
       };