diff --git a/src/utils/utf8.php b/src/utils/utf8.php
--- a/src/utils/utf8.php
+++ b/src/utils/utf8.php
@@ -426,6 +426,8 @@
  * @return list  A list of characters in the string.
  */
 function phutil_utf8v($string, $byte_limit = null) {
+  $string = phutil_string_cast($string);
+
   $res = array();
   $len = strlen($string);