diff --git a/sip/transaction.go b/sip/transaction.go
index 966838a..6e95e3c 100644
--- a/sip/transaction.go
+++ b/sip/transaction.go
@@ -103,8 +103,7 @@ type ServerTransaction interface {
 	Acks() <-chan *Request
 	// Cancels is triggered when transaction is canceled, that is SIP CANCEL is received for transaction.
 	// Cancels() <-chan *Request
-
-	OnCancel(f func(r *Request))
+	// OnCancel(f func(r *Request))
 }
 
 type ClientTransaction interface {