diff --git a/README.adoc b/README.adoc
index 7683dc8..13e37f7 100644
--- a/README.adoc
+++ b/README.adoc
@@ -52,7 +52,10 @@ sudo emaint sync -r guru
 sudo emerge -a app-text/epubgrep
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-=== Debian buster
+=== Debian and Ubuntu
+
+This repository works for Debian buster (10) and Ubuntu focal (20.04). It _may_
+work for other versions, I have not tested it.
 
 [source,shell]
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