diff --git a/FreeBSD.md b/FreeBSD.md
index e9816cb..833c3d4 100644
--- a/FreeBSD.md
+++ b/FreeBSD.md
@@ -1,3 +1,13 @@
+# Upgrade FreeBSD version to the latest
+
+Sometimes packages installed via `pkg` might not work. Even if you get an iso file from the official site, the version might not be the latest. For example, run this commend to update your FreeBSD to 11.1-RELEASE:
+
+```
+freebsd-update -r 11.1-RELEASE upgrade
+```
+
+For more detail, see [the official manual](https://www.freebsd.org/doc/handbook/updating-upgrading-freebsdupdate.html).
+
 # Set up desktop environment
 
 Ebiten requires X Window system and you need to install a window manager like gnome3. See [the official manual](https://www.freebsd.org/doc/handbook/x11-wm.html). Note that you also need to do `pkg install xorg`.