diff --git a/Dockerfile b/Dockerfile
index f464a82..8ef317f 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -12,6 +12,7 @@ RUN set -x && \
     linux-headers \
     make
 # setup the build
+ARG ARCH="amd64"
 ARG K3S_ROOT_VERSION=v0.13.0
 ADD https://github.com/rancher/k3s-root/releases/download/${K3S_ROOT_VERSION}/k3s-root-xtables-${ARCH}.tar /opt/xtables/k3s-root-xtables.tar
 RUN tar xvf /opt/xtables/k3s-root-xtables.tar -C /opt/xtables