diff --git a/Synology-NAS-Guide.md b/Synology-NAS-Guide.md
index f20fe0e..0ee7b69 100644
--- a/Synology-NAS-Guide.md
+++ b/Synology-NAS-Guide.md
@@ -43,6 +43,8 @@ In case you use another DNS service, check the `dnsapi` directory and [DNS API g
 ## Creating the certificate
 Now it's time to create the certificate for your domain:
 
+Note: Since `v3`, `acme.sh` uses Zerossl as the default Certificate Authority (CA). Account registration (one-time) is required before one can issue new certs. See: https://github.com/acmesh-official/acme.sh/wiki/ZeroSSL.com-CA
+
 ```sh
 # These commands assume you are still working in the same terminal and have ran necessary commands described above.