diff --git a/README.md b/README.md
index 15697e207a3d10582cc370f4c435e0324f043a9a..26e8f68e015c726b2d16ac807f9ad2b07f031463 100644
--- a/README.md
+++ b/README.md
@@ -56,6 +56,10 @@ Getting started
 
 - Use `git series start seriesname` to start a patch series seriesname.
 
+- Use `git series base somecommit` to set the base commit for the series.
+  (This is the upstream commit you based the series on, not the first patch in
+  the series.)
+
 - Use normal git commands to commit changes.
 
 - Use `git series status` to check what has changed.