diff --git a/draft-ymbk-idr-l3nd-ulpc.xml b/draft-ymbk-idr-l3nd-ulpc.xml
index cb11f25..202f708 100644
--- a/draft-ymbk-idr-l3nd-ulpc.xml
+++ b/draft-ymbk-idr-l3nd-ulpc.xml
@@ -219,6 +219,12 @@
       they share.  If there are multiple choices, the BGP speaker SHOULD
       have signaled which subnet to choose in an Upper-Layer Protocol
       Configuration PDU Attribute.</t>
+
+      <t>Attributes MUST be unique in the Attribute List.  I.e. a
+      particular Attr Type MUST NOT occur more than once in the
+      Attribute List.  If a ULPC PDU is received with multiple
+      occurances of the same Attr Type, an Error ACK should be
+      returned.</t>
         
 <!--
     protocol "Attr Type = 1:8,Attr Len = 6:8,My ASN:32"