diff --git a/flake.nix b/flake.nix
index 520397d1..4cc025ff 100644
--- a/flake.nix
+++ b/flake.nix
@@ -60,7 +60,7 @@
           then hostConf.ip4
           else if hostConf ? ip6
           then hostConf.ip6
-          else null;
+          else throw "Host ${name} has no ip4 or ip6 address";
     in {
       overlay = import ./overlay;