1 files changed, 4 insertions, 1 deletions
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index 5a0d819fb7..324d45fb7a 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -1829,7 +1829,10 @@ class TestModule < Test::Unit::TestCase
 
     name = "@\u{5909 6570}"
     assert_warning(/instance variable #{name} not initialized/) do
-      assert_nil(a.instance_eval(name))
+      val = EnvUtil.with_default_external(Encoding::UTF_8) {
+        a.instance_eval(name)
+      }
+      assert_nil(val)
     end
   end