diff --git a/Filer-Server-API.md b/Filer-Server-API.md
index b54fe09..4fb56d3 100644
--- a/Filer-Server-API.md
+++ b/Filer-Server-API.md
@@ -36,7 +36,7 @@ You can append to any HTTP API with &pretty=y to see a formatted json output.
 | maxMB | max chunk size | empty |
 | mode | file mode | 0660 |
 | op | file operation, currently only support "append" | empty |
-| ensureParentDir | need ensure parent directory exists | true |
+| ensureParentDir | need to ensure parent directory exists | true |
 | header: `Content-Type` | used for auto compression | empty |
 | header: `Content-Disposition` | used as response content-disposition | empty |
 | prefixed header: `Seaweed-` | example: `Seaweed-name1: value1`. Returned as `Seaweed-Name1: value1` in GET/HEAD response header. | empty |