diff --git a/comment_notify.inc b/comment_notify.inc
index e82bdc9..474e011 100644
--- a/comment_notify.inc
+++ b/comment_notify.inc
@@ -136,7 +136,7 @@ function comment_notify_add_notification($cid, $notify, $notify_hash) {
   return (bool)db_insert('comment_notify')
     ->fields(array(
       'cid' => $cid,
-      'notify' => $notify,
+      'notify' => $notify === NULL ? 0 : $notify,
       'notify_hash' => $notify_hash,
     ))
     ->execute();
@@ -164,7 +164,7 @@ function comment_notify_remove_all_notifications($cid) {
 function comment_notify_update_notification($cid, $notify) {
   return (bool)db_update('comment_notify')
     ->fields(array(
-      'notify' => $notify,
+      'notify' => $notify === NULL ? 0 : $notify,
     ))
     ->condition('cid', $cid)
     ->execute();
diff --git a/comment_notify.module b/comment_notify.module
index bbd7843..e13e25b 100644
--- a/comment_notify.module
+++ b/comment_notify.module
@@ -131,7 +131,7 @@ function comment_notify_form_comment_form_alter(&$form, &$form_state, $form_id)
   $form['notify_settings']['notify_type'] = array(
     '#type' => 'radios',
     '#options' => $available_options,
-    '#default_value' => $preference,
+    '#default_value' => $preference ? $preference : NULL,
   );
   if (count($available_options) == 1) {
     $form['notify_settings']['notify_type']['#type'] = 'hidden';