diff --git a/nix/nixos-module/container/upstream.nix b/nix/nixos-module/container/upstream.nix
index 799a3ce..9e7e2a7 100644
--- a/nix/nixos-module/container/upstream.nix
+++ b/nix/nixos-module/container/upstream.nix
@@ -67,7 +67,7 @@ in
       iptables -A fwd_smtp -j REJECT
       iptables -I FORWARD -p tcp --dport 25 -j fwd_smtp
 
-      ip6tables -N fwd_smtp \
+      ip6tables -N fwd_smtp || \
         ip6tables -F fwd_smtp
       ${lib.concatMapStrings (subnet6: ''
         ip6tables -A fwd_smtp --source ${subnet6} -j RETURN