diff --git a/build.xml b/build.xml
index 1b145c4d..e3a57880 100644
--- a/build.xml
+++ b/build.xml
@@ -856,6 +856,7 @@
                 <arg value="${build.dir}/check_idpdisc.xsl"/>
 				<arg value="${build.dir}/check_mdiop.xsl"/>
                 <arg value="${build.dir}/check_misc.xsl"/>
+				<arg value="${build.dir}/check_namespaces.xsl"/>
                 <arg value="${build.dir}/check_shibboleth.xsl"/>
 				<!-- single context-dependent ruleset -->
 				<arg value="${build.dir}/@{s}"/>
diff --git a/build/check_namespaces.xsl b/build/check_namespaces.xsl
new file mode 100644
index 00000000..8e547ed0
--- /dev/null
+++ b/build/check_namespaces.xsl
@@ -0,0 +1,81 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+	
+	check_namespaces.xsl
+	
+	Metadata checking ruleset that ensures that all namespaces used in a metadata file
+	are known to us, by flagging those which are not.
+	
+	Author: Ian A. Young <ian@iay.org.uk>
+	
+-->
+<xsl:stylesheet version="1.0"
+	xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
+	xmlns:elab="http://eduserv.org.uk/labels"
+	xmlns:idpdisc="urn:oasis:names:tc:SAML:profiles:SSO:idp-discovery-protocol"
+	xmlns:md="urn:oasis:names:tc:SAML:2.0:metadata"
+	xmlns:mdui="urn:oasis:names:tc:SAML:metadata:ui"
+	xmlns:shibmd="urn:mace:shibboleth:metadata:1.0"
+	xmlns:ukfedlabel="http://ukfederation.org.uk/2006/11/label"
+	xmlns:wayf="http://sdss.ac.uk/2006/06/WAYF"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+	xmlns="urn:oasis:names:tc:SAML:2.0:metadata">
+	
+	<!--
+		Common support functions.
+	-->
+	<xsl:import href="check_framework.xsl"/>
+	
+	<!--
+		Explicitly accept elements in namespaces which we know about.
+	-->
+	
+	<xsl:template match="ds:*">
+		<xsl:apply-templates/>
+	</xsl:template>
+	
+	<xsl:template match="elab:*">
+		<xsl:apply-templates/>
+	</xsl:template>
+	
+	<xsl:template match="idpdisc:*">
+		<xsl:apply-templates/>
+	</xsl:template>
+	
+	<xsl:template match="md:*">
+		<xsl:apply-templates/>
+	</xsl:template>
+	
+	<xsl:template match="mdui:*">
+		<xsl:apply-templates/>
+	</xsl:template>
+	
+	<xsl:template match="shibmd:*">
+		<xsl:apply-templates/>
+	</xsl:template>
+	
+	<xsl:template match="wayf:*">
+		<xsl:apply-templates/>
+	</xsl:template>
+	
+	<xsl:template match="ukfedlabel:*">
+		<xsl:apply-templates/>
+	</xsl:template>
+	
+	<!--
+		Reject elements in all other namespaces.
+	-->
+	
+	<xsl:template match="*">
+		<xsl:call-template name="fatal">
+			<xsl:with-param name="m">
+				<xsl:text>Unknown namespace: </xsl:text>
+				<xsl:value-of select="namespace-uri()"/>
+				<xsl:text> on element </xsl:text>
+				<xsl:value-of select="name()"/>
+			</xsl:with-param>
+		</xsl:call-template>
+	</xsl:template>
+	
+</xsl:stylesheet>