diff --git a/mdx/uk/add_hide_category.xsl b/mdx/uk/add_hide_category.xsl
new file mode 100644
index 00000000..164ffd88
--- /dev/null
+++ b/mdx/uk/add_hide_category.xsl
@@ -0,0 +1,66 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+	add_hide_category.xsl
+
+	Adds the REFEDS "Hide from Discovery" entity category to IdPs which are already
+	labelled with the UK federation's "HideFromWAYF" marker element.
+	
+	Assumes that the IdP in question has an Extensions element already, but no
+	entity attributes. This is currently true for UKf-registered entities, but
+	a longer term solution will require the ability to add a new value into
+	an existing collection of entity attributes.
+
+-->
+<xsl:stylesheet version="1.0"
+	xmlns:md="urn:oasis:names:tc:SAML:2.0:metadata"
+	xmlns:mdattr="urn:oasis:names:tc:SAML:metadata:attribute"
+	xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion"
+	xmlns:wayf="http://sdss.ac.uk/2006/06/WAYF"
+	
+	xmlns="urn:oasis:names:tc:SAML:2.0:metadata"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+	exclude-result-prefixes="md">
+
+	<!--Force UTF-8 encoding for the output.-->
+	<xsl:output omit-xml-declaration="no" method="xml" encoding="UTF-8" indent="yes"/>
+
+	<xsl:template match="md:EntityDescriptor[md:IDPSSODescriptor]/md:Extensions[wayf:HideFromWAYF]">
+		<xsl:copy>
+			<xsl:text>&#10;</xsl:text>
+			<xsl:text>        </xsl:text>
+			<xsl:element name="mdattr:EntityAttributes">
+				<xsl:text>&#10;</xsl:text>
+				<xsl:text>            </xsl:text>
+				<xsl:element name="saml:Attribute">
+					<xsl:attribute name="Name">http://macedir.org/entity-category</xsl:attribute>
+					<xsl:attribute name="NameFormat">urn:oasis:names:tc:SAML:2.0:attrname-format:uri</xsl:attribute>
+					<xsl:text>&#10;</xsl:text>
+					<xsl:text>                </xsl:text>
+					<xsl:element name="saml:AttributeValue">
+						<xsl:text>http://refeds.org/category/hide-from-discovery</xsl:text>
+					</xsl:element>
+					<xsl:text>&#10;</xsl:text>
+					<xsl:text>            </xsl:text>
+				</xsl:element>
+				<xsl:text>&#10;</xsl:text>
+				<xsl:text>        </xsl:text>
+			</xsl:element>
+			<xsl:apply-templates select="node()"/>
+		</xsl:copy>
+	</xsl:template>
+	
+	<!--By default, copy text blocks, comments and attributes unchanged.-->
+	<xsl:template match="text()|comment()|@*">
+		<xsl:copy/>
+	</xsl:template>
+	
+	<!--By default, copy all elements from the input to the output, along with their attributes and contents.-->
+	<xsl:template match="*">
+		<xsl:copy>
+			<xsl:apply-templates select="node()|@*"/>
+		</xsl:copy>
+	</xsl:template>
+	
+</xsl:stylesheet>
diff --git a/mdx/uk/beans.xml b/mdx/uk/beans.xml
index 6d9aa598..24e8febf 100644
--- a/mdx/uk/beans.xml
+++ b/mdx/uk/beans.xml
@@ -458,6 +458,18 @@
                 <ref bean="uk_default_regauth"/>
                 <ref bean="populateRegistrationAuthorities"/>
                 
+                <!--
+                    Add REFEDS Hide from Discovery category as a standardised
+                    equivalent to our HideFromWAYF element.
+                -->
+                <bean p:id="uk_addHideFromDiscovery" parent="XSLTransformationStage">
+                    <property name="XSLResource">
+                        <bean parent="ClassPathResource">
+                            <constructor-arg value="uk/add_hide_category.xsl"/>
+                        </bean>
+                    </property>                    
+                </bean>
+                
                 <ref bean="checkSchemas"/>
                 <ref bean="CHECK_std"/>
                 <ref bean="check_ukreg"/>
diff --git a/mdx/uk/check_uk_mdattr.xsl b/mdx/uk/check_uk_mdattr.xsl
index 47a257bc..df524d4f 100644
--- a/mdx/uk/check_uk_mdattr.xsl
+++ b/mdx/uk/check_uk_mdattr.xsl
@@ -77,6 +77,7 @@
 	-->
 	<xsl:template match="mdattr:EntityAttributes/saml:Attribute[@Name='http://macedir.org/entity-category']
 		/saml:AttributeValue
+		[. != 'http://refeds.org/category/hide-from-discovery']
 		[. != 'http://www.geant.net/uri/dataprotection-code-of-conduct/v1']
 		">
 		<xsl:call-template name="error">