diff --git a/lib/markdown_converter.rb b/lib/markdown_converter.rb
index 75bb99b..ef45934 100644
--- a/lib/markdown_converter.rb
+++ b/lib/markdown_converter.rb
@@ -569,7 +569,11 @@ def convert_li(el, indent)
         output = ' '*indent << "<#{el.type}" << html_attributes(el.attr) << ">"
 
         if el.value.respond_to?(:mark)
-          output << "<span class=\"bullet-list-marker\">(#{el.value.mark})</span>"
+          if el.value.mark.nil?
+            output << "<span class=\"bullet-list-marker\">● &nbsp;</span>"
+          else
+            output << "<span class=\"bullet-list-marker\">(#{el.value.mark})</span>"
+          end
         end
 
         res = inner(el, indent)