diff --git a/packet_packer.go b/packet_packer.go
index cf919409..3664b00c 100644
--- a/packet_packer.go
+++ b/packet_packer.go
@@ -30,6 +30,7 @@ type packetPacker struct {
 
 	controlFrames []frames.Frame
 	stopWaiting   *frames.StopWaitingFrame
+	ackFrame      *frames.AckFrame
 	leastUnacked  protocol.PacketNumber
 }
 
@@ -65,16 +66,20 @@ func (p *packetPacker) PackConnectionClose(ccf *frames.ConnectionCloseFrame) (*p
 	}, err
 }
 
-func (p *packetPacker) PackAckPacket(ackframe *frames.AckFrame) (*packedPacket, error) {
+func (p *packetPacker) PackAckPacket() (*packedPacket, error) {
+	if p.ackFrame == nil {
+		return nil, errors.New("packet packer BUG: no ack frame queued")
+	}
 	encLevel, sealer := p.cryptoSetup.GetSealer()
 	ph := p.getPublicHeader(encLevel)
-	frames := []frames.Frame{ackframe}
+	frames := []frames.Frame{p.ackFrame}
 	if p.stopWaiting != nil {
 		p.stopWaiting.PacketNumber = ph.PacketNumber
 		p.stopWaiting.PacketNumberLen = ph.PacketNumberLen
 		frames = append(frames, p.stopWaiting)
 		p.stopWaiting = nil
 	}
+	p.ackFrame = nil
 	raw, err := p.writeAndSealPacket(ph, frames, sealer)
 	return &packedPacket{
 		number:          ph.PacketNumber,
@@ -84,8 +89,8 @@ func (p *packetPacker) PackAckPacket(ackframe *frames.AckFrame) (*packedPacket,
 	}, err
 }
 
-// RetransmitNonForwardSecurePacket retransmits a handshake packet, that was sent with less than forward-secure encryption
-func (p *packetPacker) RetransmitNonForwardSecurePacket(packet *ackhandler.Packet) (*packedPacket, error) {
+// PackHandshakeRetransmission retransmits a handshake packet, that was sent with less than forward-secure encryption
+func (p *packetPacker) PackHandshakeRetransmission(packet *ackhandler.Packet) (*packedPacket, error) {
 	if packet.EncryptionLevel == protocol.EncryptionForwardSecure {
 		return nil, errors.New("PacketPacker BUG: forward-secure encrypted handshake packets don't need special treatment")
 	}
@@ -144,6 +149,7 @@ func (p *packetPacker) PackPacket() (*packedPacket, error) {
 		return nil, nil
 	}
 	p.stopWaiting = nil
+	p.ackFrame = nil
 
 	raw, err := p.writeAndSealPacket(publicHeader, payloadFrames, sealer)
 	if err != nil {
@@ -185,9 +191,24 @@ func (p *packetPacker) composeNextPacket(
 	var payloadLength protocol.ByteCount
 	var payloadFrames []frames.Frame
 
+	// STOP_WAITING and ACK will always fit
 	if p.stopWaiting != nil {
-		p.controlFrames = append(p.controlFrames, p.stopWaiting)
+		payloadFrames = append(payloadFrames, p.stopWaiting)
+		l, err := p.stopWaiting.MinLength(p.version)
+		if err != nil {
+			return nil, err
+		}
+		payloadLength += l
 	}
+	if p.ackFrame != nil {
+		payloadFrames = append(payloadFrames, p.ackFrame)
+		l, err := p.ackFrame.MinLength(p.version)
+		if err != nil {
+			return nil, err
+		}
+		payloadLength += l
+	}
+
 	for len(p.controlFrames) > 0 {
 		frame := p.controlFrames[len(p.controlFrames)-1]
 		minLength, err := frame.MinLength(p.version)
@@ -232,10 +253,13 @@ func (p *packetPacker) composeNextPacket(
 	return payloadFrames, nil
 }
 
-func (p *packetPacker) QueueControlFrameForNextPacket(f frames.Frame) {
-	if swf, ok := f.(*frames.StopWaitingFrame); ok {
-		p.stopWaiting = swf
-	} else {
+func (p *packetPacker) QueueControlFrameForNextPacket(frame frames.Frame) {
+	switch f := frame.(type) {
+	case *frames.StopWaitingFrame:
+		p.stopWaiting = f
+	case *frames.AckFrame:
+		p.ackFrame = f
+	default:
 		p.controlFrames = append(p.controlFrames, f)
 	}
 }
diff --git a/packet_packer_test.go b/packet_packer_test.go
index e5d8f6a4..d692f64d 100644
--- a/packet_packer_test.go
+++ b/packet_packer_test.go
@@ -638,7 +638,7 @@ var _ = Describe("Packet packer", func() {
 				EncryptionLevel: protocol.EncryptionUnencrypted,
 				Frames:          []frames.Frame{sf},
 			}
-			p, err := packer.RetransmitNonForwardSecurePacket(packet)
+			p, err := packer.PackHandshakeRetransmission(packet)
 			Expect(err).ToNot(HaveOccurred())
 			Expect(p.frames).To(ContainElement(sf))
 			Expect(p.frames).To(ContainElement(swf))
@@ -652,7 +652,7 @@ var _ = Describe("Packet packer", func() {
 				EncryptionLevel: protocol.EncryptionSecure,
 				Frames:          []frames.Frame{sf},
 			}
-			p, err := packer.RetransmitNonForwardSecurePacket(packet)
+			p, err := packer.PackHandshakeRetransmission(packet)
 			Expect(err).ToNot(HaveOccurred())
 			Expect(p.frames).To(ContainElement(sf))
 			Expect(p.frames).To(ContainElement(swf))
@@ -667,7 +667,7 @@ var _ = Describe("Packet packer", func() {
 				EncryptionLevel: protocol.EncryptionSecure,
 				Frames:          []frames.Frame{sf},
 			}
-			p, err := packer.RetransmitNonForwardSecurePacket(packet)
+			p, err := packer.PackHandshakeRetransmission(packet)
 			Expect(err).ToNot(HaveOccurred())
 			Expect(p.encryptionLevel).To(Equal(protocol.EncryptionSecure))
 		})
@@ -684,7 +684,7 @@ var _ = Describe("Packet packer", func() {
 					},
 				},
 			}
-			_, err := packer.RetransmitNonForwardSecurePacket(packet)
+			_, err := packer.PackHandshakeRetransmission(packet)
 			Expect(err).To(MatchError("PacketPacker BUG: packet too large"))
 		})
 
@@ -692,13 +692,13 @@ var _ = Describe("Packet packer", func() {
 			p := &ackhandler.Packet{
 				EncryptionLevel: protocol.EncryptionForwardSecure,
 			}
-			_, err := packer.RetransmitNonForwardSecurePacket(p)
+			_, err := packer.PackHandshakeRetransmission(p)
 			Expect(err).To(MatchError("PacketPacker BUG: forward-secure encrypted handshake packets don't need special treatment"))
 		})
 
 		It("refuses to retransmit packets without a StopWaitingFrame", func() {
 			packer.stopWaiting = nil
-			_, err := packer.RetransmitNonForwardSecurePacket(&ackhandler.Packet{
+			_, err := packer.PackHandshakeRetransmission(&ackhandler.Packet{
 				EncryptionLevel: protocol.EncryptionSecure,
 			})
 			Expect(err).To(MatchError("PacketPacker BUG: Handshake retransmissions must contain a StopWaitingFrame"))
@@ -707,14 +707,16 @@ var _ = Describe("Packet packer", func() {
 
 	Context("packing ACK packets", func() {
 		It("packs ACK packets", func() {
-			p, err := packer.PackAckPacket(&frames.AckFrame{})
+			packer.QueueControlFrameForNextPacket(&frames.AckFrame{})
+			p, err := packer.PackAckPacket()
 			Expect(err).NotTo(HaveOccurred())
 			Expect(p.frames).To(Equal([]frames.Frame{&frames.AckFrame{DelayTime: math.MaxInt64}}))
 		})
 
 		It("packs ACK packets with SWFs", func() {
+			packer.QueueControlFrameForNextPacket(&frames.AckFrame{})
 			packer.QueueControlFrameForNextPacket(&frames.StopWaitingFrame{})
-			p, err := packer.PackAckPacket(&frames.AckFrame{})
+			p, err := packer.PackAckPacket()
 			Expect(err).NotTo(HaveOccurred())
 			Expect(p.frames).To(Equal([]frames.Frame{
 				&frames.AckFrame{DelayTime: math.MaxInt64},
diff --git a/session.go b/session.go
index 8fd702af..1d50ac13 100644
--- a/session.go
+++ b/session.go
@@ -570,19 +570,24 @@ func (s *session) sendPacket() error {
 	for _, wuf := range windowUpdateFrames {
 		s.packer.QueueControlFrameForNextPacket(wuf)
 	}
+
+	ack := s.receivedPacketHandler.GetAckFrame()
+	if ack != nil {
+		s.packer.QueueControlFrameForNextPacket(ack)
+	}
+
 	// Repeatedly try sending until we don't have any more data, or run out of the congestion window
 	for {
 		if !s.sentPacketHandler.SendingAllowed() {
-			// If we aren't allowed to send, at least try sending an ACK frame
-			ack := s.receivedPacketHandler.GetAckFrame()
 			if ack == nil {
 				return nil
 			}
+			// If we aren't allowed to send, at least try sending an ACK frame
 			swf := s.sentPacketHandler.GetStopWaitingFrame(false)
 			if swf != nil {
 				s.packer.QueueControlFrameForNextPacket(swf)
 			}
-			packet, err := s.packer.PackAckPacket(ack)
+			packet, err := s.packer.PackAckPacket()
 			if err != nil {
 				return err
 			}
@@ -603,7 +608,7 @@ func (s *session) sendPacket() error {
 				}
 				utils.Debugf("\tDequeueing handshake retransmission for packet 0x%x", retransmitPacket.PacketNumber)
 				s.packer.QueueControlFrameForNextPacket(s.sentPacketHandler.GetStopWaitingFrame(true))
-				packet, err := s.packer.RetransmitNonForwardSecurePacket(retransmitPacket)
+				packet, err := s.packer.PackHandshakeRetransmission(retransmitPacket)
 				if err != nil {
 					return err
 				}
@@ -630,10 +635,6 @@ func (s *session) sendPacket() error {
 			}
 		}
 
-		ack := s.receivedPacketHandler.GetAckFrame()
-		if ack != nil {
-			s.packer.QueueControlFrameForNextPacket(ack)
-		}
 		hasRetransmission := s.streamFramer.HasFramesForRetransmission()
 		if ack != nil || hasRetransmission {
 			swf := s.sentPacketHandler.GetStopWaitingFrame(hasRetransmission)
@@ -654,6 +655,7 @@ func (s *session) sendPacket() error {
 			s.packer.QueueControlFrameForNextPacket(f)
 		}
 		windowUpdateFrames = nil
+		ack = nil
 		s.nextAckScheduledTime = time.Time{}
 	}
 }