diff --git a/man7/unix.7 b/man7/unix.7
index 17a10d3db..07f9e9bf3 100644
--- a/man7/unix.7
+++ b/man7/unix.7
@@ -447,12 +447,20 @@ When sending ancillary data with
 .BR sendmsg (2),
 only one item of each of the above types may be included in the sent message.
 .PP
-If the space allocated for receiving incoming ancillary data is too small,
+If the space allocated for receiving incoming ancillary data is too small
 then the ancillary data is truncated to the number of headers
 that will fit in the supplied buffer (or, in the case of an
 .BR SCM_RIGHTS
 file descriptor list, the list of file descriptors may be truncated).
-In the event of such truncation, the
+If no buffer is provided for incoming ancillary data (i.e., the
+.I msg_control
+field of the
+.I msghdr
+structure supplied to
+.BR recvmsg (2)
+is NULL),
+then the incoming ancillary data is discarded.
+In both of these cases, the
 .BR MSG_CTRUNC
 flag will be set in the
 .I msg.msg_flags