Index: /branches/release-40/lib/MT/Template/ContextHandlers.pm
===================================================================
--- /branches/release-40/lib/MT/Template/ContextHandlers.pm (revision 2556)
+++ /branches/release-40/lib/MT/Template/ContextHandlers.pm (revision 2557)
@@ -9276,4 +9276,5 @@
     my $res = '';
     my $glue = $args->{glue};
+    local $ctx->{inside_mt_categories} = 1;
     for my $cat (@$cats) {
         local $ctx->{__stash}->{category} = $cat;