diff --git a/frames/ack_frame.go b/frames/ack_frame.go
index 07cbfe13..03805414 100644
--- a/frames/ack_frame.go
+++ b/frames/ack_frame.go
@@ -27,8 +27,10 @@ type AckFrame struct {
 	LowestAcked  protocol.PacketNumber
 	AckRanges    []AckRange // has to be ordered. The ACK range with the highest FirstPacketNumber goes first, the ACK range with the lowest FirstPacketNumber goes last
 
+	// time when the LargestAcked was receiveid
+	// this field Will not be set for received ACKs frames
+	PacketReceivedTime time.Time
 	DelayTime          time.Duration
-	PacketReceivedTime time.Time // only for received packets. Will not be modified for received ACKs frames
 }
 
 // ParseAckFrame reads an ACK frame
diff --git a/frames/log.go b/frames/log.go
index 4fb1402a..1918db18 100644
--- a/frames/log.go
+++ b/frames/log.go
@@ -11,17 +11,18 @@ func LogFrame(frame Frame, sent bool) {
 	if sent {
 		dir = "->"
 	}
-	if f, ok := frame.(*StreamFrame); ok {
+	switch f := frame.(type) {
+	case *StreamFrame:
 		utils.Debugf("\t%s &frames.StreamFrame{StreamID: %d, FinBit: %t, Offset: 0x%x, Data length: 0x%x, Offset + Data length: 0x%x}", dir, f.StreamID, f.FinBit, f.Offset, f.DataLen(), f.Offset+f.DataLen())
-		return
-	}
-	if f, ok := frame.(*StopWaitingFrame); ok {
+	case *StopWaitingFrame:
 		if sent {
 			utils.Debugf("\t%s &frames.StopWaitingFrame{LeastUnacked: 0x%x, PacketNumberLen: 0x%x}", dir, f.LeastUnacked, f.PacketNumberLen)
 		} else {
 			utils.Debugf("\t%s &frames.StopWaitingFrame{LeastUnacked: 0x%x}", dir, f.LeastUnacked)
 		}
-		return
+	case *AckFrame:
+		utils.Debugf("\t%s &frames.AckFrame{LargestAcked: 0x%x, LowestAcked: 0x%x, AckRanges: %#v, DelayTime: %s}", dir, f.LargestAcked, f.LowestAcked, f.AckRanges, f.DelayTime.String())
+	default:
+		utils.Debugf("\t%s %#v", dir, frame)
 	}
-	utils.Debugf("\t%s %#v", dir, frame)
 }