diff --git a/build.xml b/build.xml
index 071c2607..620e48d5 100644
--- a/build.xml
+++ b/build.xml
@@ -1471,6 +1471,7 @@
     <property name="mda.sign.pkcs11Config" value="${sign.uk.pkcs11Config}"/>
     <property name="mda.mdq.output" value="${mdq.output.dir}"/>
     <property name="mda.validUntil.aggregate.days" value="${validUntil.aggregate.days}"/>
+    <property name="mda.validUntil.aggregate.duration" value="${validUntil.aggregate.duration}"/>
     <property name="mda.validUntil.perEntity.duration" value="${validUntil.perEntity.duration}"/>
 
     <!--
diff --git a/mdx/uk/final_tweak.xsl b/mdx/uk/final_tweak.xsl
index 0969ef29..76d4353a 100644
--- a/mdx/uk/final_tweak.xsl
+++ b/mdx/uk/final_tweak.xsl
@@ -47,27 +47,20 @@
     <xsl:param name="validityDays"/>
 
     <xsl:variable name="now" select="date:date-time()"/>
-    <xsl:variable name="validUntil" select="mdxDates:dateAdd($now, $validityDays)"/>
     <xsl:variable name="normalisedNow" select="mdxDates:dateAdd($now, 0)"/>
 
-    <!--
-        Document root.
-    -->
-    <xsl:template match="/">
-        <xsl:call-template name="document.comment"/>
-        <xsl:apply-templates/>
-    </xsl:template>
-
     <!--
         Document element.
     -->
     <xsl:template match="/md:EntitiesDescriptor">
+        <xsl:call-template name="document.comment">
+            <xsl:with-param name="validUntil" select="@validUntil"/>
+        </xsl:call-template>
         <EntitiesDescriptor>
-            <xsl:attribute name="validUntil">
-                <xsl:value-of select="$validUntil"/>
-            </xsl:attribute>
             <xsl:apply-templates select="@*"/>
-            <xsl:call-template name="document.comment"/>
+            <xsl:call-template name="document.comment">
+                <xsl:with-param name="validUntil" select="@validUntil"/>
+            </xsl:call-template>
 
             <!--
                 Add an Extensions element if there isn't one, but we need one
@@ -92,6 +85,7 @@
         Comment to be added to the top of the document, and just inside the document element.
     -->
     <xsl:template name="document.comment">
+        <xsl:param name="validUntil"/>
         <xsl:text>&#10;</xsl:text>
         <xsl:comment>
             <xsl:text>&#10;&#9;U K   F E D E R A T I O N   M E T A D A T A&#10;</xsl:text>
diff --git a/mdx/uk/generate.xml b/mdx/uk/generate.xml
index 4f140d1c..76bfad38 100644
--- a/mdx/uk/generate.xml
+++ b/mdx/uk/generate.xml
@@ -37,6 +37,19 @@
         *****************************
     -->
 
+    <!-- This bean MUST be called "conversionService" to work properly. -->
+    <bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
+        <property name="converters">
+            <set>
+                <bean class="net.shibboleth.ext.spring.config.DurationToLongConverter" />
+                <bean class="net.shibboleth.ext.spring.config.StringToIPRangeConverter" />
+                <bean class="net.shibboleth.ext.spring.config.BooleanToPredicateConverter" />
+                <bean class="net.shibboleth.ext.spring.config.StringBooleanToPredicateConverter" />
+                <bean class="net.shibboleth.ext.spring.config.StringToResourceConverter" />
+            </set>
+        </property>
+    </bean>
+
     <!--
         stripEntityScopes
 
@@ -55,6 +68,20 @@
     <bean id="finalise_parent" abstract="true" parent="mda.XSLTransformationStage"
         p:XSLResource="classpath:uk/final_tweak.xsl"/>
 
+    <!--
+        assembleAggregate
+
+        Assemble a UK-style aggregate with an appropriate validUntil.
+    -->
+    <bean id="assembleAggregate" parent="mda.CompositeStage">
+        <property name="composedStages">
+            <list>
+                <ref bean="uk_assemble"/>
+                <bean parent="mda.SetValidUntilStage" p:validityDuration="${validUntil.aggregate.duration}"/>
+            </list>
+        </property>
+    </bean>
+
     <!--
         checkPublishable
 
@@ -274,7 +301,7 @@
                 <ref bean="check_dup_display"/>
                 <ref bean="errorTerminatingFilter"/>
 
-                <ref bean="uk_assemble"/>
+                <ref bean="assembleAggregate"/>
                 <ref bean="uk_finaliseProduction"/>
                 <ref bean="setStaticID"/>
                 <ref bean="uk_normaliseNamespaces"/>
@@ -335,7 +362,7 @@
                 <ref bean="check_dup_display"/>
                 <ref bean="errorTerminatingFilter"/>
 
-                <ref bean="uk_assemble"/>
+                <ref bean="assembleAggregate"/>
 
                 <!--
                     Remove embedded images used in mdui:Logo elements.
@@ -452,7 +479,7 @@
                 <ref bean="errorTerminatingFilter"/>
 
                 <!-- make an aggregate first so that we're only traversing one item -->
-                <ref bean="uk_assemble"/>
+                <ref bean="assembleAggregate"/>
 
                 <!-- remove many things that the CDS doesn't look at -->
                 <ref bean="CDSStripUnwanted"/>
@@ -516,7 +543,7 @@
                 <ref bean="check_dup_display"/>
                 <ref bean="errorTerminatingFilter"/>
 
-                <ref bean="uk_assemble"/>
+                <ref bean="assembleAggregate"/>
                 <ref bean="stripEmptyExtensions"/>
                 <ref bean="uk_finaliseFallback"/>
                 <ref bean="setStaticID"/>
@@ -571,7 +598,7 @@
                 <ref bean="errorTerminatingFilter"/>
 
                 <ref bean="uk_strip_UKFederationMember"/>
-                <ref bean="uk_assemble"/>
+                <ref bean="assembleAggregate"/>
                 <ref bean="stripEntityScopes"/>
                 <ref bean="uk_finaliseTest"/>
                 <ref bean="setStaticID"/>
@@ -696,7 +723,7 @@
                 <ref bean="errorTerminatingFilter"/>
 
                 <ref bean="stripUkfedlabelNamespace"/>
-                <ref bean="uk_assemble"/>
+                <ref bean="assembleAggregate"/>
                 <ref bean="stripEntityScopes"/>
                 <ref bean="stripEmptyExtensions"/>
                 <ref bean="uk_finaliseExport"/>
@@ -812,7 +839,7 @@
                 <ref bean="errorTerminatingFilter"/>
 
                 <ref bean="stripUkfedlabelNamespace"/>
-                <ref bean="uk_assemble"/>
+                <ref bean="assembleAggregate"/>
                 <ref bean="stripEntityScopes"/>
                 <ref bean="stripEmptyExtensions"/>
                 <ref bean="uk_finaliseExport"/>