diff --git a/lib/nntp/tiny/message.py b/lib/nntp/tiny/message.py
index e949486..8083ce4 100644
--- a/lib/nntp/tiny/message.py
+++ b/lib/nntp/tiny/message.py
@@ -111,6 +111,8 @@ class Message(DatabaseTable):
     def unique_id(self) -> str:
         return self.header('Message-ID')
 
+    def parent_id(self) -> str:
+        return self.header('References')
 
     def date(self):
         try: