diff --git a/nixos/modules/virtualisation/incus.nix b/nixos/modules/virtualisation/incus.nix
index 47483b84872d..e1283afe8ad9 100644
--- a/nixos/modules/virtualisation/incus.nix
+++ b/nixos/modules/virtualisation/incus.nix
@@ -288,7 +288,7 @@ in
         assertion =
           !(
             config.networking.firewall.enable
-            && !config.networking.nftables.enable
+            && !(config.networking.nftables.enable || config.networking.firewall.backend == "nftables")
             && config.virtualisation.incus.enable
           );
         message = "Incus on NixOS is unsupported using iptables. Set `networking.nftables.enable = true;`";