diff --git a/xep.ent b/xep.ent
index 0bf4d191..7f97d2aa 100644
--- a/xep.ent
+++ b/xep.ent
@@ -271,6 +271,7 @@
 <!ENTITY rfc1123 "<span class='ref'><link url='http://tools.ietf.org/html/rfc1123'>RFC 1123</link></span> <note>RFC 1123: Requirements for Internet Hosts -- Application and Support &lt;<link url='http://tools.ietf.org/html/rfc1123'>http://tools.ietf.org/html/rfc1123</link>&gt;.</note>" >
 <!ENTITY rfc1305 "<span class='ref'><link url='http://tools.ietf.org/html/rfc1305'>RFC 1305</link></span> <note>RFC 1305: Network Time Protocol (Version 3) &lt;<link url='http://tools.ietf.org/html/rfc1305'>http://tools.ietf.org/html/rfc1305</link>&gt;.</note>" >
 <!ENTITY rfc1321 "<span class='ref'><link url='http://tools.ietf.org/html/rfc1321'>RFC 1321</link></span> <note>RFC 1321: The MD5 Message-Digest Algorithm &lt;<link url='http://tools.ietf.org/html/rfc1321'>http://tools.ietf.org/html/rfc1321</link>&gt;.</note>" >
+<!ENTITY rfc1393 "<span class='ref'><link url='http://tools.ietf.org/html/rfc1393'>RFC 1393</link></span> <note>RFC 1393: Traceroute Using an IP Option &lt;<link url='http://tools.ietf.org/html/rfc1393'>http://tools.ietf.org/html/rfc1393</link>&gt;.</note>" >
 <!ENTITY rfc1459 "<span class='ref'><link url='http://tools.ietf.org/html/rfc1459'>RFC 1459</link></span> <note>RFC 1459: Internet Relay Chat &lt;<link url='http://tools.ietf.org/html/rfc1459'>http://tools.ietf.org/html/rfc1459</link>&gt;.</note>" >
 <!ENTITY rfc1464 "<span class='ref'><link url='http://tools.ietf.org/html/rfc1464'>RFC 1464</link></span> <note>RFC 1464: Using the Domain Name System To Store Arbitrary String Attributes &lt;<link url='http://tools.ietf.org/html/rfc1464'>http://tools.ietf.org/html/rfc1464</link>&gt;.</note>" >
 <!ENTITY rfc1750 "<span class='ref'><link url='http://tools.ietf.org/html/rfc1750'>RFC 1750</link></span> <note>RFC 1750: Randomness Recommendations for Security &lt;<link url='http://tools.ietf.org/html/rfc1750'>http://tools.ietf.org/html/rfc1750</link>&gt;.</note>" >