diff --git a/share/sgml/freebsd.ent b/share/sgml/freebsd.ent
index 0360234304..85e08a466d 100644
--- a/share/sgml/freebsd.ent
+++ b/share/sgml/freebsd.ent
@@ -15,6 +15,7 @@
   Use this entity when refering to 'UNIX' in your document.
 -->
 <!ENTITY unix "<trademark class='registered'>UNIX</trademark>">
+<!ENTITY nis "<acronym role='Network Information System'>NIS</acronym>">
 
 <!-- Use an entity to define these exactly so that the print output
      stylesheets know what to look for and can format these properly with