diff --git a/lib/rdoc/markup/attribute_manager.rb b/lib/rdoc/markup/attribute_manager.rb
index 3296d17af2..6edb30b867 100644
--- a/lib/rdoc/markup/attribute_manager.rb
+++ b/lib/rdoc/markup/attribute_manager.rb
@@ -246,7 +246,7 @@ def add_special pattern, name
   # Processes +str+ converting attributes, HTML and specials
 
   def flow str
-    @str = str
+    @str = str.dup
 
     mask_protected_sequences
 
diff --git a/test/test_rdoc_markup_attribute_manager.rb b/test/test_rdoc_markup_attribute_manager.rb
index c0f7666a01..b51e422474 100644
--- a/test/test_rdoc_markup_attribute_manager.rb
+++ b/test/test_rdoc_markup_attribute_manager.rb
@@ -332,6 +332,14 @@ def test_protect
                   @am.flow("\\_cat_<i>dog</i>"))
   end
 
+  def test_lost_tag_for_the_second_time
+    str = "cat <tt>dog</tt>"
+    assert_equal(["cat ", @tt_on, "dog", @tt_off],
+                 @am.flow(str))
+    assert_equal(["cat ", @tt_on, "dog", @tt_off],
+                 @am.flow(str))
+  end
+
   def test_special
     @am.add_special(RDoc::CrossReference::CROSSREF_REGEXP, :CROSSREF)