diff --git a/README.md b/README.md
index 2c854828..3449e28b 100644
--- a/README.md
+++ b/README.md
@@ -60,12 +60,12 @@ The main Docker repo URL, common between Debian and RHEL systems.
     docker_apt_repository: "deb [arch={{ docker_apt_arch }}] {{ docker_repo_url }}/{{ ansible_distribution | lower }} {{ ansible_distribution_release }} {{ docker_apt_release_channel }}"
     docker_apt_ignore_key_error: True
     docker_apt_gpg_key: "{{ docker_repo_url }}/{{ ansible_distribution | lower }}/gpg"
-    docker_apt_filename: ""
+    docker_apt_filename: "docker"
 
 (Used only for Debian/Ubuntu.) You can switch the channel to `nightly` if you want to use the Nightly release.
 
 You can change `docker_apt_gpg_key` to a different url if you are behind a firewall or provide a trustworthy mirror.
-Usually in combination with changing `docker_apt_repository` as well.
+Usually in combination with changing `docker_apt_repository` as well. `docker_apt_filename` controls the name of the source list file created in `sources.list.d`. If you are upgrading from an older (<7.0.0) version of this role, you should change this to the name of the existing file (e.g. `download_docker_com_linux_debian` on Debian) to avoid conflicting lists.
 
     docker_yum_repo_url: "{{ docker_repo_url }}/{{ (ansible_distribution == 'Fedora') | ternary('fedora','centos') }}/docker-{{ docker_edition }}.repo"docker_edition }}.repo
     docker_yum_repo_enable_nightly: '0'