diff --git a/docs/developer_guides/chap08_binlog.md b/docs/developer_guides/chap08_binlog.md
index 92fb5c3cdd..654739a604 100644
--- a/docs/developer_guides/chap08_binlog.md
+++ b/docs/developer_guides/chap08_binlog.md
@@ -8,7 +8,7 @@ Schema column records the DDL of the collection.
 
 ## Event format
 
-Binlog file consists of 4 bytes magic number and a series of events. The first event must be descriptor event.
+Binlog file consists of 4 bytes magic number and a series of events. The first event must be a descriptor event.
 
 ### 8.1 Event format