diff --git a/nixos/modules/services/networking/flannel.nix b/nixos/modules/services/networking/flannel.nix
index c19e51e5aa6c..6ed4f78ddc92 100644
--- a/nixos/modules/services/networking/flannel.nix
+++ b/nixos/modules/services/networking/flannel.nix
@@ -92,10 +92,8 @@ in {
         Needed when running with Kubernetes as backend as this cannot be auto-detected";
       '';
       type = types.nullOr types.str;
-      default = with config.networking; (hostName + optionalString (domain != null) ".${domain}");
-      defaultText = literalExpression ''
-        with config.networking; (hostName + optionalString (domain != null) ".''${domain}")
-      '';
+      default = config.networking.fqdnOrHostName;
+      defaultText = literalExpression "config.networking.fqdnOrHostName";
       example = "node1.example.com";
     };