Index: src/wp-includes/comment.php
===================================================================
--- src/wp-includes/comment.php	(revision 35855)
+++ src/wp-includes/comment.php	(working copy)
@@ -1496,7 +1496,7 @@
 	$comment_date     = ! isset( $data['comment_date'] )     ? current_time( 'mysql' )            : $data['comment_date'];
 	$comment_date_gmt = ! isset( $data['comment_date_gmt'] ) ? get_gmt_from_date( $comment_date ) : $data['comment_date_gmt'];

-	$comment_post_ID  = ! isset( $data['comment_post_ID'] )  ? '' : $data['comment_post_ID'];
+	$comment_post_ID  = ! isset( $data['comment_post_ID'] )  ? 0  : $data['comment_post_ID'];
 	$comment_content  = ! isset( $data['comment_content'] )  ? '' : $data['comment_content'];
 	$comment_karma    = ! isset( $data['comment_karma'] )    ? 0  : $data['comment_karma'];
 	$comment_approved = ! isset( $data['comment_approved'] ) ? 1  : $data['comment_approved'];