diff --git a/test/test_rdoc_parser.rb b/test/test_rdoc_parser.rb
index b9bff9c327..01cff30067 100644
--- a/test/test_rdoc_parser.rb
+++ b/test/test_rdoc_parser.rb
@@ -231,6 +231,17 @@ def test_class_use_markup
     assert_equal @RP::RD, parser
   end
 
+  def test_class_use_markup_rdoc
+    content = <<-CONTENT
+# :markup: RDoc
+    CONTENT
+
+    parser = @RP.use_markup content
+
+    assert_nil parser
+  end
+
+
   def test_class_use_markup_markdown
     content = <<-CONTENT
 # coding: utf-8 markup: markdown