diff --git a/schema/lib/elements/he_ipv6.xsd b/schema/lib/elements/he_ipv6.xsd
index db6dc60..69bbb0e 100644
--- a/schema/lib/elements/he_ipv6.xsd
+++ b/schema/lib/elements/he_ipv6.xsd
@@ -33,14 +33,14 @@
             </xs:element>
           </xs:sequence>
         </xs:complexType>
-        <xs:unique name="uniq_alloc_prefix">
-          <xs:selector xpath="alloc"/>
-          <xs:field xpath="@prefix"/>
-        </xs:unique>
         <xs:unique name="uniq_alloc_addr">
-          <xs:selector xpath="alloc"/>
+          <xs:selector xpath=".//*"/>
           <xs:field xpath="."/>
         </xs:unique>
+        <xs:unique name="uniq_alloc_prefix">
+          <xs:selector xpath=".//*"/>
+          <xs:field xpath="@prefix"/>
+        </xs:unique>
       </xs:element>
       <xs:element name="client" minOccurs="1" maxOccurs="1">
         <xs:complexType>
diff --git a/schema/projects/he_ipv6.xsd b/schema/projects/he_ipv6.xsd
index 2dc2e25..535b22f 100644
--- a/schema/projects/he_ipv6.xsd
+++ b/schema/projects/he_ipv6.xsd
@@ -33,6 +33,13 @@
         </xs:element>
       </xs:all>
     </xs:complexType>
+    <!--
+    I have tried and tried to do document-wide unique constraints of alloc addrs and client addrs etc., but to no avail.
+    I keep getting e.g.:
+      Element '{http://www.w3.org/2001/XMLSchema}selector', attribute 'xpath': The XPath expression
+      '//heIPv6:alloc' could not be compiled.
+    So it's not idiot-proof.
+    -->
   </xs:element>
 
 </xs:schema>