diff --git a/doc/api/fs.md b/doc/api/fs.md
index 8077c533f854d2..2f1ce3f4876d2a 100644
--- a/doc/api/fs.md
+++ b/doc/api/fs.md
@@ -5031,6 +5031,12 @@ The following constants are meant for use with `fs.open()`.
O_NONBLOCK
Flag indicating to open the file in nonblocking mode when possible.
+
+
UV_FS_O_FILEMAP
+
When set, a memory file mapping is used to access the file. This flag
+ is available on Windows operating systems only. On other operating systems,
+ this flag is ignored.