diff --git a/share/man/man5/tmpfs.5 b/share/man/man5/tmpfs.5
index 8fff1c15815..bf07f06de02 100644
--- a/share/man/man5/tmpfs.5
+++ b/share/man/man5/tmpfs.5
@@ -154,6 +154,9 @@ main memory and swap space) will be used.
 .It Cm uid
 Set the user ID of the root inode of the file system.
 The default is the mount point's UID.
+.It Cm union
+Refer to
+.Xr mount 8 .
 .El
 .Sh EXAMPLES
 Mount a