diff --git a/docs/04-certificate-authority.md b/docs/04-certificate-authority.md
index 7229356..6d7faf7 100644
--- a/docs/04-certificate-authority.md
+++ b/docs/04-certificate-authority.md
@@ -62,6 +62,8 @@ ca-key.pem
 ca.pem
 ```
 
+(A third file, `ca.csr`, is also generated, but can be ignored.)
+
 ## Client and Server Certificates
 
 In this section you will generate client and server certificates for each Kubernetes component and a client certificate for the Kubernetes `admin` user.