diff --git a/core/template.php b/core/template.php
index ee5df08..262003c 100644
--- a/core/template.php
+++ b/core/template.php
@@ -178,7 +178,14 @@ function om_process_html(&$variables) {
         $page_type_op = $node_type . '-' . arg(2);        
       }      
     }
-    $classes[] = om_id_safe('section-' . $section) . ' ' . om_id_safe('page-' . $page_type) . ' ' . om_id_safe('page-' . $page_type_op);
+    $classes_str = om_id_safe('section-' . $section) . ' ' . om_id_safe('page-' . $page_type);
+
+    if (isset($page_type_op)){
+      $classes_str .= ' ' . om_id_safe('page-' . $page_type_op);
+    }
+
+    $classes[] = $classes_str;
+
   }
   $variables['classes_array'] = $classes;
   $variables['classes'] = implode(' ', $classes); // Concatenate with spaces.