diff -u b/core/includes/theme.inc b/core/includes/theme.inc
--- b/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1244,7 +1244,6 @@
     $variables['rows'][] = array(array(
       'data' => $variables['empty'],
       'colspan' => $header_count,
-      'class' => array('empty', 'message'),
     ));
   }
 
@@ -1264,6 +1263,7 @@
     $variables['rows'][] = array(array(
       'data' => $variables['empty'],
       'colspan' => $header_count,
+      'class' => array('empty', 'message'),
     ));
   }
 
diff -u b/core/modules/system/templates/table.html.twig b/core/modules/system/templates/table.html.twig
--- b/core/modules/system/templates/table.html.twig
+++ b/core/modules/system/templates/table.html.twig
@@ -63,7 +63,7 @@
               cell.table_sort ? 'active',
             ]
           %}
-          <{{ cell.tag }}{{ cell.attributes.addclass(cell_classes) }}>
+          <{{ cell.tag }}{{ cell.attributes.addClass(cell_classes) }}>
             {{- cell.content -}}
           </{{ cell.tag }}>
         {% endfor %}