diff --git a/includes/unicode.inc b/includes/unicode.inc
index f9684a8..9ca3adf 100644
--- a/includes/unicode.inc
+++ b/includes/unicode.inc
@@ -525,4 +525,8 @@
  */
 function drupal_strtolower($text) {
+  if (!is_string($text)) {
+    return $text;
+  }
+  
   global $multibyte;
   if ($multibyte == UNICODE_MULTIBYTE) {