diff --git a/tools/mkimage-iso-bios/Dockerfile b/tools/mkimage-iso-bios/Dockerfile
index 12b0fef6e..be78af6a6 100644
--- a/tools/mkimage-iso-bios/Dockerfile
+++ b/tools/mkimage-iso-bios/Dockerfile
@@ -1,13 +1,16 @@
-FROM linuxkit/alpine:daed76b8f1d28cdeeee215a95b9671c682a405dc
-
-RUN \
-  apk update && apk upgrade && \
-  apk add --no-cache \
-  libarchive-tools \
-  cdrkit \
-  syslinux \
-  && true
+FROM linuxkit/alpine:daed76b8f1d28cdeeee215a95b9671c682a405dc as mirror
+RUN mkdir -p /out/etc/apk && cp -r /etc/apk/* /out/etc/apk/
+RUN apk add --no-cache --initdb -p /out \
+    alpine-baselayout \
+    busybox \
+    cdrkit \
+    libarchive-tools \
+    syslinux \
+    && true
+RUN mv /out/etc/apk/repositories.upstream /out/etc/apk/repositories
 
+FROM scratch
+WORKDIR /
+COPY --from=mirror /out/ /
 COPY . .
-
 ENTRYPOINT [ "/make-iso" ]