diff --git a/etc/emqx.conf b/etc/emqx.conf
index 6f28bf59d..14414b220 100644
--- a/etc/emqx.conf
+++ b/etc/emqx.conf
@@ -417,7 +417,7 @@ log.file = emqx.log
 ##
 ## Value: Number
 ## Default: 10M
-## Supported Unit: KB | MB | G
+## Supported Unit: KB | MB | GB
 log.rotation.size = 10MB
 
 ## Maximum rotation count of log files.