Index: branches/release-33/php/lib/function.mtarchivecount.php
===================================================================
--- branches/release-33/php/lib/function.mtarchivecount.php (revision 1747)
+++ branches/release-33/php/lib/function.mtarchivecount.php (revision 1750)
@@ -14,5 +14,6 @@
         $archiver = $_archivers[$at];
     }
-    if ($ctx->stash('inside_mt_categories') && !$archiver->is_date_based()) {
+    if ((!$archiver && $ctx->stash('inside_mt_categories')) ||
+        ($ctx->stash('inside_mt_categories') && !$archiver->is_date_based())) {
         return $ctx->tag('MTCategoryCount', $args);
     } elseif ($count = $ctx->stash('archive_count')) {