diff --git a/nix/nixos-module/container/upstream.nix b/nix/nixos-module/container/upstream.nix
index b502d39..6e86dd8 100644
--- a/nix/nixos-module/container/upstream.nix
+++ b/nix/nixos-module/container/upstream.nix
@@ -20,10 +20,7 @@ in
       # systemd-networkd only requests Prefix Delegation via DHCPv6 on
       # the upstream interface if another interface is configured for it.
       # without this, the static ipv6 subnet won't be routed to us.
-      extraConfig = ''
-        [Network]
-        IPv6PrefixDelegation=dhcpv6
-      '';
+      networkConfig.DHCPv6PrefixDelegation = true;
       dhcpV6PrefixDelegationConfig = {
         SubnetId = "81";
         # because we have static addresses, we don't actually use this