2 files changed, 21 insertions, 1 deletions
diff --git a/error.c b/error.c
index ffdd1a4ef1..7f9e582930 100644
--- a/error.c
+++ b/error.c
@@ -329,7 +329,13 @@ rb_warn_m(int argc, VALUE *argv, VALUE exc)
 	    rb_io_puts(argc, argv, str);
 	    RBASIC_SET_CLASS(str, rb_cString);
 	}
-	rb_write_warning_str(str);
+	if (exc == rb_mWarning) {
+	    rb_must_asciicompat(str);
+	    rb_write_error_str(str);
+	}
+	else {
+	    rb_write_warning_str(str);
+	}
     }
     return Qnil;
 }
diff --git a/test/ruby/test_exception.rb b/test/ruby/test_exception.rb
index bcad728789..3622cae0d9 100644
--- a/test/ruby/test_exception.rb
+++ b/test/ruby/test_exception.rb
@@ -1034,6 +1034,20 @@ $stderr = $stdout; raise "\x82\xa0"') do |outs, errs, status|
     assert_match(/^\tfrom #{Regexp.escape(path)}:1:/, warning.first)
   end
 
+  def test_warning_warn_super
+    assert_in_out_err(%[-W0], "#{<<~"{#"}\n#{<<~'};'}", [], /instance variable @a not initialized/)
+    {#
+      module Warning
+        def warn(message)
+          super
+        end
+      end
+
+      $VERBOSE = true
+      @a
+    };
+  end
+
   def test_undefined_backtrace
     assert_separately([], "#{<<-"begin;"}\n#{<<-"end;"}")
     begin;