diff --git a/nix/nixos-module/container/upstream/pppoe.nix b/nix/nixos-module/container/upstream/pppoe.nix
index 424a99d..b3af6e4 100644
--- a/nix/nixos-module/container/upstream/pppoe.nix
+++ b/nix/nixos-module/container/upstream/pppoe.nix
@@ -65,7 +65,7 @@ in lib.mkIf (pppoeInterfaces != {}) {
       "${ifName}" = {
         matchConfig.Name = "${ifName}";
         networkConfig = {
-          DHCP = lib.mkOverride 900 "ipv6";
+          DHCP = lib.mkForce "ipv6";
           # accept config set by pppd
           KeepConfiguration = "yes";
         };