diff --git a/lib/redmine_dmsf/webdav/base_resource.rb b/lib/redmine_dmsf/webdav/base_resource.rb
index 7b5bf7ae..cf5841fb 100644
--- a/lib/redmine_dmsf/webdav/base_resource.rb
+++ b/lib/redmine_dmsf/webdav/base_resource.rb
@@ -95,7 +95,7 @@ module RedmineDmsf
 
       def parent
         p = @__proxy.parent
-        return nil unless p
+        return nil if p.nil? 
         return p.resource.nil? ? p : p.resource
       end
 
@@ -160,4 +160,4 @@ table { width:100%%; }
       end
     end
   end
-end
\ No newline at end of file
+end