diff --git a/Dockerfile b/Dockerfile
index 953f30f..cd39d36 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -36,7 +36,7 @@ RUN \
 ADD https://github.com/just-containers/s6-overlay/releases/download/v${BUILD_S6_OVERLAY_VERSION}/s6-overlay-noarch.tar.xz /tmp
 RUN tar -C /root-out -Jxpf /tmp/s6-overlay-noarch.tar.xz
 ADD https://github.com/just-containers/s6-overlay/releases/download/v${BUILD_S6_OVERLAY_VERSION}/s6-overlay-${BUILD_S6_ARCH_amd64}.tar.xz /tmp
-RUN tar -C /root-out -Jxpf /tmp/s6-overlay-${S6_ARCH_amd64}.tar.xz
+RUN tar -C /root-out -Jxpf /tmp/s6-overlay-${BUILD_S6_ARCH_amd64}.tar.xz
 
 # add s6 optional symlinks
 ADD https://github.com/just-containers/s6-overlay/releases/download/v${BUILD_S6_OVERLAY_VERSION}/s6-overlay-symlinks-noarch.tar.xz /tmp
diff --git a/Dockerfile.aarch64 b/Dockerfile.aarch64
index a908c01..e5465ca 100644
--- a/Dockerfile.aarch64
+++ b/Dockerfile.aarch64
@@ -36,7 +36,7 @@ RUN \
 ADD https://github.com/just-containers/s6-overlay/releases/download/v${BUILD_S6_OVERLAY_VERSION}/s6-overlay-noarch.tar.xz /tmp
 RUN tar -C /root-out -Jxpf /tmp/s6-overlay-noarch.tar.xz
 ADD https://github.com/just-containers/s6-overlay/releases/download/v${BUILD_S6_OVERLAY_VERSION}/s6-overlay-${S6_ARCH_aarch64}.tar.xz /tmp
-RUN tar -C /root-out -Jxpf /tmp/s6-overlay-${S6_ARCH_aarch64}.tar.xz
+RUN tar -C /root-out -Jxpf /tmp/s6-overlay-${BUILD_S6_ARCH_aarch64}.tar.xz
 
 # add s6 optional symlinks
 ADD https://github.com/just-containers/s6-overlay/releases/download/v${BUILD_S6_OVERLAY_VERSION}/s6-overlay-symlinks-noarch.tar.xz /tmp