diff --git a/wp-admin/admin-ajax.php b/wp-admin/admin-ajax.php
index 2351958b85..df75c17140 100644
--- a/wp-admin/admin-ajax.php
+++ b/wp-admin/admin-ajax.php
@@ -1473,8 +1473,10 @@ case 'set-post-thumbnail':
 	check_ajax_referer( "set_post_thumbnail-$post_ID" );
 
 	if ( $thumbnail_id == '-1' ) {
-		delete_post_meta( $post_ID, '_thumbnail_id' );
-		die( _wp_post_thumbnail_html() );
+		if ( delete_post_thumbnail( $post_ID ) )
+			die( _wp_post_thumbnail_html() );
+		else
+			die( '0' );
 	}
 
 	if ( set_post_thumbnail( $post_ID, $thumbnail_id ) )
diff --git a/wp-includes/post.php b/wp-includes/post.php
index 93bdb0a36b..091ebaccbd 100644
--- a/wp-includes/post.php
+++ b/wp-includes/post.php
@@ -5190,6 +5190,21 @@ function set_post_thumbnail( $post, $thumbnail_id ) {
 	return false;
 }
 
+/**
+ * Removes a post thumbnail.
+ *
+ * @since 3.3.0
+ *
+ * @param int|object $post Post ID or object where thumbnail should be removed from.
+ * @return bool True on success, false on failure.
+ */
+function delete_post_thumbnail( $post ) {
+	$post = get_post( $post );
+	if ( $post )
+		return delete_post_meta( $post->ID, '_thumbnail_id' );
+	return false;
+}
+
 /**
  * Returns a link to a post format index.
  *