diff --git a/share/sgml/trademarks.ent b/share/sgml/trademarks.ent
index ad3a97899e..ac0b30782d 100644
--- a/share/sgml/trademarks.ent
+++ b/share/sgml/trademarks.ent
@@ -239,6 +239,8 @@
   registered trademarks and IT DialTone and The Open Group are
   trademarks of The Open Group in the United States and other
   countries.</para>">
+<!ENTITY tm-attrib.unix "<para>UNIX is a registered trademarks of The
+  Open Group in the United States and other countries.</para>">
 <!ENTITY motif "<trademark class='registered'>Motif</trademark>">
 <!ENTITY unix "<trademark class='registered'>UNIX</trademark>">