diff --git a/man2/recv.2 b/man2/recv.2
index 7b04f89d2..5b403594c 100644
--- a/man2/recv.2
+++ b/man2/recv.2
@@ -78,8 +78,9 @@ With a zero
 .I flags
 argument,
 .BR recv ()
-is equivalent to
-.BR read (2).
+is generally equivalent to
+.BR read (2)
+(but see NOTES).
 Also, the following call
 
     recv(sockfd, buf, len, flags);
@@ -515,6 +516,19 @@ and
 .B MSG_WAITALL
 flags.
 .SH NOTES
+If a zero-length datagram is pending,
+.BR read (2)
+and
+.BR recv ()
+with a
+.I flags
+argument of zero provide different behavior.
+In this circumstance,
+.BR read (2)
+has no effect (the datagram remains pending), while
+.BR recv ()
+consumes the pending datagram.
+
 The
 .I socklen_t
 type was invented by POSIX.