diff --git a/docs/public/certbot/index.rst b/docs/public/certbot/index.rst
index 0845ee4..09b6bfe 100644
--- a/docs/public/certbot/index.rst
+++ b/docs/public/certbot/index.rst
@@ -7,7 +7,8 @@ DNS certificate
 .. code:: shell
 
  mkdir tmp
- DOMAIN=domain.tld certbot \
+ DOMAIN='domain.tld'
+ certbot \
  --config-dir tmp \
  --logs-dir tmp \
  --work-dir tmp \