diff --git a/build.xml b/build.xml
index 8180a1d7..5ba3e43d 100644
--- a/build.xml
+++ b/build.xml
@@ -918,4 +918,16 @@
 		</exec>
 	</target>
 	
+	<!--
+	   Check for IdPs using the single-port configuration.
+	   
+	   It just so happens that the check_imported ruleset is exactly what we want
+	   right now.
+	-->
+	<target name="check.ports" depends="gen.uk.master">
+		<echo>Checking vhost use</echo>
+        <CHECK i="${xml.dir}/${uk.master.file}" s="check_imported.xsl"/>
+        <echo>Checked.</echo>
+	</target>
+
 </project>
\ No newline at end of file