diff --git a/ci/Dockerfile-test.el6 b/ci/Dockerfile-test.el6
index 837a6095b..918651dd7 100644
--- a/ci/Dockerfile-test.el6
+++ b/ci/Dockerfile-test.el6
@@ -1,2 +1,3 @@
+ARG DOCKER_ARCH
 FROM --platform=linux/${DOCKER_ARCH} centos:6
 RUN yum -y install curl