diff --git a/frames/ack_frame.go b/frames/ack_frame.go
index e78cb7cd1..a1fda41e2 100644
--- a/frames/ack_frame.go
+++ b/frames/ack_frame.go
@@ -14,7 +14,6 @@ type AckFrame struct {
 	Entropy         byte
 	LargestObserved protocol.PacketNumber
 	DelayTime       uint16 // Todo: properly interpret this value as described in the specification
-	HasNACK         bool
 	NackRanges      []*ackhandler.NackRange
 }
 
@@ -31,6 +30,14 @@ func (f *AckFrame) Write(b *bytes.Buffer) error {
 	return nil
 }
 
+// HasNACK returns if the frame has NACK ranges
+func (f *AckFrame) HasNACK() bool {
+	if len(f.NackRanges) > 0 {
+		return true
+	}
+	return false
+}
+
 // ParseAckFrame reads an ACK frame
 func ParseAckFrame(r *bytes.Reader) (*AckFrame, error) {
 	frame := &AckFrame{}
@@ -40,9 +47,9 @@ func ParseAckFrame(r *bytes.Reader) (*AckFrame, error) {
 		return nil, err
 	}
 
-	frame.HasNACK = false
+	hasNACK := false
 	if typeByte&0x20 == 0x20 {
-		frame.HasNACK = true
+		hasNACK = true
 	}
 	if typeByte&0x10 == 0x10 {
 		panic("truncated ACKs not yet implemented.")
@@ -105,7 +112,7 @@ func ParseAckFrame(r *bytes.Reader) (*AckFrame, error) {
 		}
 	}
 
-	if frame.HasNACK {
+	if hasNACK {
 		var numRanges uint8
 		numRanges, err = r.ReadByte()
 		if err != nil {
diff --git a/frames/ack_frame_test.go b/frames/ack_frame_test.go
index 23e260310..67fb15204 100644
--- a/frames/ack_frame_test.go
+++ b/frames/ack_frame_test.go
@@ -17,7 +17,7 @@ var _ = Describe("AckFrame", func() {
 			Expect(frame.Entropy).To(Equal(byte(0xA4)))
 			Expect(frame.LargestObserved).To(Equal(protocol.PacketNumber(0x03)))
 			Expect(frame.DelayTime).To(Equal(uint16(0x4523)))
-			Expect(frame.HasNACK).To(Equal(false))
+			Expect(frame.HasNACK()).To(Equal(false))
 			Expect(b.Len()).To(Equal(0))
 		})
 
@@ -40,7 +40,7 @@ var _ = Describe("AckFrame", func() {
 			b := bytes.NewReader([]byte{0x60, 0x8, 0x3, 0x72, 0x1, 0x1, 0x0, 0xc0, 0x15, 0x0, 0x0, 0x1, 0x1, 0x1})
 			frame, err := ParseAckFrame(b)
 			Expect(err).ToNot(HaveOccurred())
-			Expect(frame.HasNACK).To(Equal(true))
+			Expect(frame.HasNACK()).To(Equal(true))
 			Expect(len(frame.NackRanges)).To(Equal(1))
 			Expect(frame.NackRanges[0].FirstPacketNumber).To(Equal(protocol.PacketNumber(1)))
 			Expect(frame.NackRanges[0].Length).To(Equal(uint8(2)))
@@ -50,7 +50,7 @@ var _ = Describe("AckFrame", func() {
 			b := bytes.NewReader([]byte{0x60, 0x2, 0xf, 0xb8, 0x1, 0x1, 0x0, 0xe5, 0x58, 0x4, 0x0, 0x3, 0x1, 0x6, 0x1, 0x2, 0x1, 0x0})
 			frame, err := ParseAckFrame(b)
 			Expect(err).ToNot(HaveOccurred())
-			Expect(frame.HasNACK).To(Equal(true))
+			Expect(frame.HasNACK()).To(Equal(true))
 			Expect(len(frame.NackRanges)).To(Equal(3))
 			Expect(frame.NackRanges[0].FirstPacketNumber).To(Equal(protocol.PacketNumber(8)))
 			Expect(frame.NackRanges[0].Length).To(Equal(uint8(7)))