diff --git a/docs/api/session.md b/docs/api/session.md
index 78b001fdab..91ff30ad6a 100644
--- a/docs/api/session.md
+++ b/docs/api/session.md
@@ -20,17 +20,25 @@ const ses = win.webContents.session
 
 The `session` module has the following methods:
 
-### session.fromPartition(partition)
+### session.fromPartition(partition[, options])
 
 * `partition` String
+* `options` Object
+  * `cache` Boolean - Whether to enable cache.
 
-Returns a new `Session` instance from `partition` string.
+Returns a `Session` instance from `partition` string. When there is an existing
+`Session` with the same `partition`, it will be returned; othewise a new
+`Session` instance will be created with `options`.
 
 If `partition` starts with `persist:`, the page will use a persistent session
 available to all pages in the app with the same `partition`. if there is no
 `persist:` prefix, the page will use an in-memory session. If the `partition` is
 empty then default session of the app will be returned.
 
+To create a `Session` with `options`, you have to ensure the `Session` with the
+`partition` has never been used before. There is no way to change the `options`
+of an existing `Session` object.
+
 ## Properties
 
 The `session` module has the following properties: