diff --git a/bootstraptest/test_syntax.rb b/bootstraptest/test_syntax.rb
index 8b499c50d5..3e4c79bece 100644
--- a/bootstraptest/test_syntax.rb
+++ b/bootstraptest/test_syntax.rb
@@ -626,5 +626,5 @@ assert_equal '2', %q{
 
 assert_match /illegal multibyte char/, %q{
   STDERR.reopen(STDOUT)
-  eval("\"\xfd".force_encoding("utf-8"))
+  eval("\"\xf0".force_encoding("utf-8"))
 }, '[ruby-dev:32429]'