diff --git a/mailnews/news/public/nsINNTPNewsgroupPost.idl b/mailnews/news/public/nsINNTPNewsgroupPost.idl
index e1c45890a950..573a54ff6bbc 100644
--- a/mailnews/news/public/nsINNTPNewsgroupPost.idl
+++ b/mailnews/news/public/nsINNTPNewsgroupPost.idl
@@ -41,7 +41,7 @@ interface nsINNTPNewsgroupPost : nsISupports {
     readonly attribute string messageID;
     attribute string path;
 
-    boolean IsValid();
+    boolean isValid();
     
     /* Secion 2.2 - optional headers */
     attribute string replyTo;