diff --git a/README.md b/README.md
index 9519bf74..dbb4b8e0 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,7 @@ material in a different way; see the [Preface](Preface).
 
 In directory `sf/` run the following:
 
+    $ make clobber              (remove all files before rebuilding system)
     $ make macos-setup          (might need sudo, but try it without first)
     $ make build                (builds lagda->markdown and website)
     $ make build-incremental    (builds lagda->markdown and website using incremental)