diff --git a/includes/form.inc b/includes/form.inc
index b564797..66783c7 100644
--- a/includes/form.inc
+++ b/includes/form.inc
@@ -3069,7 +3069,7 @@ function form_process_checkboxes($element) {
         '#type' => 'checkbox',
         '#title' => $choice,
         '#return_value' => $key,
-        '#default_value' => isset($value[$key]) ? $key : NULL,
+        '#default_value' => isset($value[$key]) || (is_array($element['#default_value']) && in_array($key, $element['#default_value'])) ? $key : NULL,
         '#attributes' => $element['#attributes'],
         '#ajax' => isset($element['#ajax']) ? $element['#ajax'] : NULL,
         '#weight' => $weight,