diff --git a/includes/theme.inc b/includes/theme.inc
index 5a6026a..97a6093 100644
--- a/includes/theme.inc
+++ b/includes/theme.inc
@@ -2108,6 +2108,8 @@ function theme_username($variables) {
 /**
  * Returns HTML for a progress bar.
  *
+ * Note that the core Batch API uses this only for non-JavaScript batch jobs.
+ *
  * @param $variables
  *   An associative array containing:
  *   - percent: The percentage of the progress.