diff --git a/Dockerfile b/Dockerfile
index 97534dc..e023e34 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -8,6 +8,7 @@ ENV UBUNTU_MIRROR_ARCHITECTURES amd64
 ENV UBUNTU_ENABLE_SOURCE_MIRRORING false
 ENV UBUNTU_MIRROR_CATEGORIES main,universe,restricted,multiverse,main/debian-installer
 ENV UBUNTU_MIRROR_UPSTREAM archive.ubuntu.com
+ENV UBUNTU_MIRROR_UPSTREAM_PATH /ubuntu
 ENV UBUNTU_MIRROR_PROJECTS bionic,bionic-updates,bionic-security,bionic-backports,focal,focal-updates,focal-security,focal-backports
 
 # The following is the URL populated in /mirrors.txt as used by mirror://