diff --git a/mdx/_rules/check_mdui_logo_length.xsl b/mdx/_rules/check_mdui_logo_length.xsl
new file mode 100644
index 00000000..11ee3fcf
--- /dev/null
+++ b/mdx/_rules/check_mdui_logo_length.xsl
@@ -0,0 +1,52 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    check_mdui_logo_length.xsl
+
+    Checking ruleset to generate warnings for mdui:Logo elements with
+    lengths longer than a provided threshold.
+-->
+<xsl:stylesheet version="1.0"
+    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+    xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
+    xmlns:md="urn:oasis:names:tc:SAML:2.0:metadata"
+    xmlns:mdui="urn:oasis:names:tc:SAML:metadata:ui"
+    xmlns:mdxURL="xalan://uk.ac.sdss.xalan.md.URLchecker"
+    xmlns:set="http://exslt.org/sets"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns="urn:oasis:names:tc:SAML:2.0:metadata">
+
+    <!--
+        Common support functions.
+    -->
+    <xsl:import href="check_framework.xsl"/>
+
+    <!--
+        maxLength
+
+        This parameter determines the maximum allowable mdui:Logo length
+        before we issue a warning.
+    -->
+    <xsl:param name="maxLength"/>
+
+    <!--
+        Match mdui:Logo elements whose string length is greater than the
+        threshold value; issue a warning for them.
+
+        Template match expressions can't include parameter references, so
+        match all mdui:Logo elements then dig in with a conditional.
+    -->
+    <xsl:template match="mdui:Logo">
+        <xsl:if test="string-length(.) > $maxLength">
+            <xsl:call-template name="warning">
+                <xsl:with-param name="m">
+                    <xsl:text>mdui:Logo has long contents: </xsl:text>
+                    <xsl:value-of select="string-length(.)"/>
+                    <xsl:text> > </xsl:text>
+                    <xsl:value-of select="$maxLength"/>
+                </xsl:with-param>
+            </xsl:call-template>
+        </xsl:if>
+    </xsl:template>
+
+</xsl:stylesheet>
diff --git a/mdx/validation-beans.xml b/mdx/validation-beans.xml
index 980bd328..c0553f12 100644
--- a/mdx/validation-beans.xml
+++ b/mdx/validation-beans.xml
@@ -220,6 +220,21 @@
     <bean id="check_mdui_xslt" parent="mda.XSLValidationStage"
         p:XSLResource="classpath:_rules/check_mdui.xsl"/>
 
+    <!--
+        check_mdui_logo_length
+
+        Add a warning for mdui:Logo elements longer than some
+        threshold.
+    -->
+    <bean id="check_mdui_logo_length" parent="mda.XSLValidationStage"
+        p:XSLResource="classpath:_rules/check_mdui_logo_length.xsl">
+        <property name="transformParameters">
+            <map>
+                <entry key="maxLength" value="${mdui.logo.length.warn:40000}"/>
+            </map>
+        </property>
+    </bean>
+
     <!--
         check_mdui
 
@@ -230,6 +245,7 @@
             <list>
                 <ref bean="check_mdui_iphint"/>
                 <ref bean="check_mdui_xslt"/>
+                <ref bean="check_mdui_logo_length"/>
             </list>
         </property>
     </bean>