diff --git a/man7/unix.7 b/man7/unix.7
index 79f93899c..a8efc8940 100644
--- a/man7/unix.7
+++ b/man7/unix.7
@@ -467,6 +467,15 @@ see
 The specified local address is already in use or the filesystem socket
 object already exists.
 .TP
+.B EBADF
+This error can occur for
+.BR sendmsg (2)
+when sending a file descriptor as ancillary data over
+a UNIX domain socket (see the description of
+.BR SCM_RIGHTS ,
+above), and indicates that the file descriptor number that
+is being sent is not valid (e.g., it is not an open file descripror).
+.TP
 .B ECONNREFUSED
 The remote address specified by
 .BR connect (2)