diff --git a/docs/MultiISP.xml b/docs/MultiISP.xml
index a8d664f01..830817c64 100644
--- a/docs/MultiISP.xml
+++ b/docs/MultiISP.xml
@@ -237,6 +237,22 @@
                 low-order 8 bits being zero).</para>
               </listitem>
             </itemizedlist>
+
+            <warning>
+              <para>A bug in Shorewall versions 3.2, 3.4 and 4.0 prevents
+              proper handling of PREROUTING marks when HIGH_ROUTE_MARKS=No.
+              Patches are available to correct this problem:</para>
+
+              <para>Shorewall version 3.2.0-3.4.3: <ulink
+              url="http://www1.shorewall.net/pub/shorewall/3.2/shorewall-3.2.10/errata/patches/Shorewall/patch-3.2.10-2.diff">http://www1.shorewall.net/pub/shorewall/3.2/shorewall-3.2.10/errata/patches/Shorewall/patch-3.2.10-2.diff
+              </ulink></para>
+
+              <para>Shorewall version 3.4.4-3.4.6: <ulink
+              url="http://www1.shorewall.net/pub/shorewall/3.4/shorewall-3.4.6/errata/patches/Shorewall/patch-3.4.6-1.diff">http://www1.shorewall.net/pub/shorewall/3.4/shorewall-3.4.6/errata/patches/Shorewall/patch-3.4.6-1.diff</ulink></para>
+
+              <para>Shorewall-shell version 4.0.0-4.0.2: <ulink
+              url="http://www1.shorewall.net/pub/shorewall/4.0/shorewall-4.0.2/errata/patches/Shorewall-shell/patch-shell-4.0.2-2.diff">http://www1.shorewall.net/pub/shorewall/4.0/shorewall-4.0.2/errata/patches/Shorewall-shell/patch-shell-4.0.2-2.diff</ulink></para>
+            </warning>
           </listitem>
         </varlistentry>