diff --git a/backup/util/helper/convert_helper.class.php b/backup/util/helper/convert_helper.class.php
index 98e1ed0eafa..a2d16b6e553 100644
--- a/backup/util/helper/convert_helper.class.php
+++ b/backup/util/helper/convert_helper.class.php
@@ -145,9 +145,11 @@ abstract class convert_helper {
         $firstchars = fread($handle, 200);
         $status     = fclose($handle);
 
-        if (strpos($firstchars,'<?xml version="1.0" encoding="UTF-8"?>') !== false and
-            strpos($firstchars,'<moodle_backup>') !== false and
-            strpos($firstchars,'<information>') !== false) {
+        // Look for expected XML elements (case-insensitive to account for encoding attribute).
+        if (stripos($firstchars, '<?xml version="1.0" encoding="UTF-8"?>') !== false &&
+            strpos($firstchars, '<moodle_backup>') !== false &&
+            strpos($firstchars, '<information>') !== false) {
+
                 return true;
         }