diff --git a/mailnews/base/public/nsIMsgHdr.idl b/mailnews/base/public/nsIMsgHdr.idl
index 867ae7904543..47cadc937e4e 100644
--- a/mailnews/base/public/nsIMsgHdr.idl
+++ b/mailnews/base/public/nsIMsgHdr.idl
@@ -71,6 +71,8 @@ interface nsIMsgHdr : nsISupports
   readonly attribute unsigned long messageOffset;
   readonly attribute unsigned long statusOffset;
   readonly attribute string charSet;
+
+  void MarkRead(in boolean markRead);
   
 };