diff --git a/usr.bin/xinstall/install.1 b/usr.bin/xinstall/install.1
--- a/usr.bin/xinstall/install.1
+++ b/usr.bin/xinstall/install.1
@@ -234,8 +234,9 @@
 unlinks an existing target before installing the new file.
 With the
 .Fl S
-flag a temporary file is used and then renamed to be
-the target.
+flag a temporary file is used,
+.Xr fsync 2
+-ed, and then renamed to be the target.
 The reason this is safer is that if the copy or
 rename fails, the existing target is left untouched.
 .It Fl s