diff --git a/README.md b/README.md
index 033eb8e..c3455d2 100644
--- a/README.md
+++ b/README.md
@@ -3,3 +3,6 @@
 How I put my very own personal servers online, for free.
 
 Details at [the blog post](http://ralsina.me/weblog/posts/the-cheapest-server.html)
+
+When adding a new hostname, remember to create a cert for it using
+`flyctl certs create hostname`