diff --git a/modules/comment.module b/modules/comment.module
index 0fce40d1400f01eab5611be73a9877dec8882788..a16d31c1a19bdcc9af37d59b14b41a5844968740 100644
--- a/modules/comment.module
+++ b/modules/comment.module
@@ -1188,7 +1188,7 @@ function comment_form($edit, $title = NULL) {
   }
 
   if ($op == t('Preview comment')) {
-    $form['#post_process'] = 'comment_form_add_preview';
+    $form['#after_build'] = 'comment_form_add_preview';
   }
 
   if ($_REQUEST['destination']) {
diff --git a/modules/comment/comment.module b/modules/comment/comment.module
index 0fce40d1400f01eab5611be73a9877dec8882788..a16d31c1a19bdcc9af37d59b14b41a5844968740 100644
--- a/modules/comment/comment.module
+++ b/modules/comment/comment.module
@@ -1188,7 +1188,7 @@ function comment_form($edit, $title = NULL) {
   }
 
   if ($op == t('Preview comment')) {
-    $form['#post_process'] = 'comment_form_add_preview';
+    $form['#after_build'] = 'comment_form_add_preview';
   }
 
   if ($_REQUEST['destination']) {