Index: wp-includes/pluggable.php
===================================================================
--- wp-includes/pluggable.php	(revision 11972)
+++ wp-includes/pluggable.php	(working copy)
@@ -1560,6 +1560,8 @@
 				$email = $user->user_email;
 		} elseif ( !empty($id_or_email->comment_author_email) ) {
 			$email = $id_or_email->comment_author_email;
+		} elseif ( !empty($id_or_email->comment_author_IP) ) {
+			$email = $id_or_email->comment_author_IP;
 		}
 	} else {
 		$email = $id_or_email;