diff --git a/lib/tests/moodlelib_test.php b/lib/tests/moodlelib_test.php
index 0abcc021c3e..3124b326987 100644
--- a/lib/tests/moodlelib_test.php
+++ b/lib/tests/moodlelib_test.php
@@ -179,6 +179,7 @@ class moodlelib_test extends \advanced_testcase {
 
         // Invalid utf8 string.
         $this->assertSame('aš', fix_utf8('a'.chr(130).'š'), 'This fails with buggy iconv() when mbstring extenstion is not available as fallback.');
+        $this->assertSame('Hello ', fix_utf8('Hello ￿'));
     }
 
     public function test_optional_param() {