diff --git a/tcpdf.php b/tcpdf.php
index 0ee30bc..582a418 100644
--- a/tcpdf.php
+++ b/tcpdf.php
@@ -12382,7 +12382,7 @@ class TCPDF {
 			$x = $this->w;
 		}
 		$fixed = false;
-		if (!empty($page) AND ($page[0] == '*')) {
+		if ((string)$page && (((string)$page)[0] == '*')) {
 			$page = intval(substr($page, 1));
 			// this page number will not be changed when moving/add/deleting pages
 			$fixed = true;