diff --git a/framer.go b/framer.go
index fbfe9bb7..d5be6fc9 100644
--- a/framer.go
+++ b/framer.go
@@ -12,7 +12,7 @@ type framer interface {
 	AppendControlFrames([]wire.Frame, protocol.ByteCount) ([]wire.Frame, protocol.ByteCount)
 
 	AddActiveStream(protocol.StreamID)
-	AppendStreamFrames([]wire.Frame, protocol.ByteCount) []wire.Frame
+	AppendStreamFrames([]wire.Frame, protocol.ByteCount) ([]wire.Frame, protocol.ByteCount)
 }
 
 type framerI struct {
@@ -73,7 +73,7 @@ func (f *framerI) AddActiveStream(id protocol.StreamID) {
 	f.mutex.Unlock()
 }
 
-func (f *framerI) AppendStreamFrames(frames []wire.Frame, maxLen protocol.ByteCount) []wire.Frame {
+func (f *framerI) AppendStreamFrames(frames []wire.Frame, maxLen protocol.ByteCount) ([]wire.Frame, protocol.ByteCount) {
 	var length protocol.ByteCount
 	f.mutex.Lock()
 	// pop STREAM frames, until less than MinStreamFrameSize bytes are left in the packet
@@ -105,5 +105,5 @@ func (f *framerI) AppendStreamFrames(frames []wire.Frame, maxLen protocol.ByteCo
 		length += frame.Length(f.version)
 	}
 	f.mutex.Unlock()
-	return frames
+	return frames, length
 }
diff --git a/framer_test.go b/framer_test.go
index 214528d7..075bb6d2 100644
--- a/framer_test.go
+++ b/framer_test.go
@@ -85,8 +85,9 @@ var _ = Describe("Stream Framer", func() {
 			}
 			stream1.EXPECT().popStreamFrame(gomock.Any()).Return(f, false)
 			framer.AddActiveStream(id1)
-			fs := framer.AppendStreamFrames(nil, 1000)
+			fs, length := framer.AppendStreamFrames(nil, 1000)
 			Expect(fs).To(Equal([]wire.Frame{f}))
+			Expect(length).To(Equal(f.Length(version)))
 		})
 
 		It("appends to a frame slice", func() {
@@ -99,8 +100,9 @@ var _ = Describe("Stream Framer", func() {
 			framer.AddActiveStream(id1)
 			mdf := &wire.MaxDataFrame{ByteOffset: 1337}
 			frames := []wire.Frame{mdf}
-			fs := framer.AppendStreamFrames(frames, 1000)
+			fs, length := framer.AppendStreamFrames(frames, 1000)
 			Expect(fs).To(Equal([]wire.Frame{mdf, f}))
+			Expect(length).To(Equal(f.Length(version)))
 		})
 
 		It("skips a stream that was reported active, but was completed shortly after", func() {
@@ -113,7 +115,8 @@ var _ = Describe("Stream Framer", func() {
 			stream2.EXPECT().popStreamFrame(gomock.Any()).Return(f, false)
 			framer.AddActiveStream(id1)
 			framer.AddActiveStream(id2)
-			Expect(framer.AppendStreamFrames(nil, 1000)).To(Equal([]wire.Frame{f}))
+			frames, _ := framer.AppendStreamFrames(nil, 1000)
+			Expect(frames).To(Equal([]wire.Frame{f}))
 		})
 
 		It("skips a stream that was reported active, but doesn't have any data", func() {
@@ -127,7 +130,8 @@ var _ = Describe("Stream Framer", func() {
 			stream2.EXPECT().popStreamFrame(gomock.Any()).Return(f, false)
 			framer.AddActiveStream(id1)
 			framer.AddActiveStream(id2)
-			Expect(framer.AppendStreamFrames(nil, 1000)).To(Equal([]wire.Frame{f}))
+			frames, _ := framer.AppendStreamFrames(nil, 1000)
+			Expect(frames).To(Equal([]wire.Frame{f}))
 		})
 
 		It("pops from a stream multiple times, if it has enough data", func() {
@@ -137,10 +141,13 @@ var _ = Describe("Stream Framer", func() {
 			stream1.EXPECT().popStreamFrame(gomock.Any()).Return(f1, true)
 			stream1.EXPECT().popStreamFrame(gomock.Any()).Return(f2, false)
 			framer.AddActiveStream(id1) // only add it once
-			Expect(framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize)).To(Equal([]wire.Frame{f1}))
-			Expect(framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize)).To(Equal([]wire.Frame{f2}))
+			frames, _ := framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize)
+			Expect(frames).To(Equal([]wire.Frame{f1}))
+			frames, _ = framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize)
+			Expect(frames).To(Equal([]wire.Frame{f2}))
 			// no further calls to popStreamFrame, after popStreamFrame said there's no more data
-			Expect(framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize)).To(BeNil())
+			frames, _ = framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize)
+			Expect(frames).To(BeNil())
 		})
 
 		It("re-queues a stream at the end, if it has enough data", func() {
@@ -155,11 +162,14 @@ var _ = Describe("Stream Framer", func() {
 			framer.AddActiveStream(id1) // only add it once
 			framer.AddActiveStream(id2)
 			// first a frame from stream 1
-			Expect(framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize)).To(Equal([]wire.Frame{f11}))
+			frames, _ := framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize)
+			Expect(frames).To(Equal([]wire.Frame{f11}))
 			// then a frame from stream 2
-			Expect(framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize)).To(Equal([]wire.Frame{f2}))
+			frames, _ = framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize)
+			Expect(frames).To(Equal([]wire.Frame{f2}))
 			// then another frame from stream 1
-			Expect(framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize)).To(Equal([]wire.Frame{f12}))
+			frames, _ = framer.AppendStreamFrames(nil, protocol.MinStreamFrameSize)
+			Expect(frames).To(Equal([]wire.Frame{f12}))
 		})
 
 		It("only dequeues data from each stream once per packet", func() {
@@ -172,7 +182,9 @@ var _ = Describe("Stream Framer", func() {
 			stream2.EXPECT().popStreamFrame(gomock.Any()).Return(f2, true)
 			framer.AddActiveStream(id1)
 			framer.AddActiveStream(id2)
-			Expect(framer.AppendStreamFrames(nil, 1000)).To(Equal([]wire.Frame{f1, f2}))
+			frames, length := framer.AppendStreamFrames(nil, 1000)
+			Expect(frames).To(Equal([]wire.Frame{f1, f2}))
+			Expect(length).To(Equal(f1.Length(version) + f2.Length(version)))
 		})
 
 		It("returns multiple normal frames in the order they were reported active", func() {
@@ -184,7 +196,8 @@ var _ = Describe("Stream Framer", func() {
 			stream2.EXPECT().popStreamFrame(gomock.Any()).Return(f2, false)
 			framer.AddActiveStream(id2)
 			framer.AddActiveStream(id1)
-			Expect(framer.AppendStreamFrames(nil, 1000)).To(Equal([]wire.Frame{f2, f1}))
+			frames, _ := framer.AppendStreamFrames(nil, 1000)
+			Expect(frames).To(Equal([]wire.Frame{f2, f1}))
 		})
 
 		It("only asks a stream for data once, even if it was reported active multiple times", func() {
@@ -193,12 +206,14 @@ var _ = Describe("Stream Framer", func() {
 			stream1.EXPECT().popStreamFrame(gomock.Any()).Return(f, false) // only one call to this function
 			framer.AddActiveStream(id1)
 			framer.AddActiveStream(id1)
-			Expect(framer.AppendStreamFrames(nil, 1000)).To(HaveLen(1))
+			frames, _ := framer.AppendStreamFrames(nil, 1000)
+			Expect(frames).To(HaveLen(1))
 		})
 
 		It("does not pop empty frames", func() {
-			fs := framer.AppendStreamFrames(nil, 500)
+			fs, length := framer.AppendStreamFrames(nil, 500)
 			Expect(fs).To(BeEmpty())
+			Expect(length).To(BeZero())
 		})
 
 		It("pops frames that have the minimum size", func() {
@@ -222,8 +237,9 @@ var _ = Describe("Stream Framer", func() {
 			}
 			stream1.EXPECT().popStreamFrame(protocol.ByteCount(500)).Return(f, false)
 			framer.AddActiveStream(id1)
-			fs := framer.AppendStreamFrames(nil, 500)
+			fs, length := framer.AppendStreamFrames(nil, 500)
 			Expect(fs).To(Equal([]wire.Frame{f}))
+			Expect(length).To(Equal(f.Length(version)))
 		})
 	})
 })
diff --git a/mock_frame_source_test.go b/mock_frame_source_test.go
index e2f682a8..676da023 100644
--- a/mock_frame_source_test.go
+++ b/mock_frame_source_test.go
@@ -51,11 +51,12 @@ func (mr *MockFrameSourceMockRecorder) AppendControlFrames(arg0, arg1 interface{
 }
 
 // AppendStreamFrames mocks base method
-func (m *MockFrameSource) AppendStreamFrames(arg0 []wire.Frame, arg1 protocol.ByteCount) []wire.Frame {
+func (m *MockFrameSource) AppendStreamFrames(arg0 []wire.Frame, arg1 protocol.ByteCount) ([]wire.Frame, protocol.ByteCount) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "AppendStreamFrames", arg0, arg1)
 	ret0, _ := ret[0].([]wire.Frame)
-	return ret0
+	ret1, _ := ret[1].(protocol.ByteCount)
+	return ret0, ret1
 }
 
 // AppendStreamFrames indicates an expected call of AppendStreamFrames
diff --git a/packet_packer.go b/packet_packer.go
index bc994b54..69684556 100644
--- a/packet_packer.go
+++ b/packet_packer.go
@@ -25,6 +25,11 @@ type packer interface {
 	ChangeDestConnectionID(protocol.ConnectionID)
 }
 
+type payload struct {
+	frames []wire.Frame
+	length protocol.ByteCount
+}
+
 type packedPacket struct {
 	header *wire.ExtendedHeader
 	raw    []byte
@@ -104,7 +109,7 @@ type sealingManager interface {
 }
 
 type frameSource interface {
-	AppendStreamFrames([]wire.Frame, protocol.ByteCount) []wire.Frame
+	AppendStreamFrames([]wire.Frame, protocol.ByteCount) ([]wire.Frame, protocol.ByteCount)
 	AppendControlFrames([]wire.Frame, protocol.ByteCount) ([]wire.Frame, protocol.ByteCount)
 }
 
@@ -165,10 +170,13 @@ func newPacketPacker(
 
 // PackConnectionClose packs a packet that ONLY contains a ConnectionCloseFrame
 func (p *packetPacker) PackConnectionClose(ccf *wire.ConnectionCloseFrame) (*packedPacket, error) {
-	frames := []wire.Frame{ccf}
+	payload := payload{
+		frames: []wire.Frame{ccf},
+		length: ccf.Length(p.version),
+	}
 	encLevel, sealer := p.cryptoSetup.GetSealer()
 	header := p.getHeader(encLevel)
-	return p.writeAndSealPacket(header, frames, encLevel, sealer)
+	return p.writeAndSealPacket(header, payload, encLevel, sealer)
 }
 
 func (p *packetPacker) MaybePackAckPacket() (*packedPacket, error) {
@@ -176,11 +184,14 @@ func (p *packetPacker) MaybePackAckPacket() (*packedPacket, error) {
 	if ack == nil {
 		return nil, nil
 	}
+	payload := payload{
+		frames: []wire.Frame{ack},
+		length: ack.Length(p.version),
+	}
 	// TODO(#1534): only pack ACKs with the right encryption level
 	encLevel, sealer := p.cryptoSetup.GetSealer()
 	header := p.getHeader(encLevel)
-	frames := []wire.Frame{ack}
-	return p.writeAndSealPacket(header, frames, encLevel, sealer)
+	return p.writeAndSealPacket(header, payload, encLevel, sealer)
 }
 
 // PackRetransmission packs a retransmission
@@ -247,7 +258,7 @@ func (p *packetPacker) PackRetransmission(packet *ackhandler.Packet) ([]*packedP
 		if sf, ok := frames[len(frames)-1].(*wire.StreamFrame); ok {
 			sf.DataLenPresent = false
 		}
-		p, err := p.writeAndSealPacket(header, frames, encLevel, sealer)
+		p, err := p.writeAndSealPacket(header, payload{frames: frames, length: length}, encLevel, sealer)
 		if err != nil {
 			return nil, err
 		}
@@ -275,19 +286,21 @@ func (p *packetPacker) PackPacket() (*packedPacket, error) {
 	}
 
 	maxSize := p.maxPacketSize - protocol.ByteCount(sealer.Overhead()) - headerLen
-	frames, err := p.composeNextPacket(maxSize)
+	payload, err := p.composeNextPacket(maxSize)
 	if err != nil {
 		return nil, err
 	}
 
 	// Check if we have enough frames to send
-	if len(frames) == 0 {
+	if len(payload.frames) == 0 {
 		return nil, nil
 	}
 	// check if this packet only contains an ACK
-	if !ackhandler.HasAckElicitingFrames(frames) {
+	if !ackhandler.HasAckElicitingFrames(payload.frames) {
 		if p.numNonAckElicitingAcks >= protocol.MaxNonAckElicitingAcks {
-			frames = append(frames, &wire.PingFrame{})
+			ping := &wire.PingFrame{}
+			payload.frames = append(payload.frames, ping)
+			payload.length += ping.Length(p.version)
 			p.numNonAckElicitingAcks = 0
 		} else {
 			p.numNonAckElicitingAcks++
@@ -296,7 +309,7 @@ func (p *packetPacker) PackPacket() (*packedPacket, error) {
 		p.numNonAckElicitingAcks = 0
 	}
 
-	return p.writeAndSealPacket(header, frames, encLevel, sealer)
+	return p.writeAndSealPacket(header, payload, encLevel, sealer)
 }
 
 func (p *packetPacker) maybePackCryptoPacket() (*packedPacket, error) {
@@ -336,11 +349,12 @@ func (p *packetPacker) maybePackCryptoPacket() (*packedPacket, error) {
 	if hasData {
 		cf := s.PopCryptoFrame(p.maxPacketSize - hdrLen - protocol.ByteCount(sealer.Overhead()) - length)
 		frames = append(frames, cf)
+		length += cf.Length(p.version)
 	}
-	return p.writeAndSealPacket(hdr, frames, encLevel, sealer)
+	return p.writeAndSealPacket(hdr, payload{frames: frames, length: length}, encLevel, sealer)
 }
 
-func (p *packetPacker) composeNextPacket(maxFrameSize protocol.ByteCount) ([]wire.Frame, error) {
+func (p *packetPacker) composeNextPacket(maxFrameSize protocol.ByteCount) (payload, error) {
 	var length protocol.ByteCount
 	var frames []wire.Frame
 
@@ -360,14 +374,15 @@ func (p *packetPacker) composeNextPacket(maxFrameSize protocol.ByteCount) ([]wir
 	// the length is encoded to either 1 or 2 bytes
 	maxFrameSize++
 
-	frames = p.framer.AppendStreamFrames(frames, maxFrameSize-length)
+	frames, lengthAdded = p.framer.AppendStreamFrames(frames, maxFrameSize-length)
 	if len(frames) > 0 {
 		lastFrame := frames[len(frames)-1]
 		if sf, ok := lastFrame.(*wire.StreamFrame); ok {
 			sf.DataLenPresent = false
 		}
+		length += lengthAdded
 	}
-	return frames, nil
+	return payload{frames: frames, length: length}, nil
 }
 
 func (p *packetPacker) getHeader(encLevel protocol.EncryptionLevel) *wire.ExtendedHeader {
@@ -401,12 +416,13 @@ func (p *packetPacker) getHeader(encLevel protocol.EncryptionLevel) *wire.Extend
 
 func (p *packetPacker) writeAndSealPacket(
 	header *wire.ExtendedHeader,
-	frames []wire.Frame,
+	payload payload,
 	encLevel protocol.EncryptionLevel,
 	sealer handshake.Sealer,
 ) (*packedPacket, error) {
 	packetBuffer := getPacketBuffer()
 	buffer := bytes.NewBuffer(packetBuffer.Slice[:0])
+	frames := payload.frames
 
 	addPaddingForInitial := p.perspective == protocol.PerspectiveClient && header.Type == protocol.PacketTypeInitial
 
@@ -419,11 +435,7 @@ func (p *packetPacker) writeAndSealPacket(
 			header.Length = protocol.ByteCount(header.PacketNumberLen) + protocol.MinInitialPacketSize - headerLen
 		} else {
 			// long header packets always use 4 byte packet number, so we never need to pad short payloads
-			length := protocol.ByteCount(sealer.Overhead()) + protocol.ByteCount(header.PacketNumberLen)
-			for _, frame := range frames {
-				length += frame.Length(p.version)
-			}
-			header.Length = length
+			header.Length = protocol.ByteCount(sealer.Overhead()) + protocol.ByteCount(header.PacketNumberLen) + payload.length
 		}
 	}
 
diff --git a/packet_packer_test.go b/packet_packer_test.go
index fae6389a..222f4ccb 100644
--- a/packet_packer_test.go
+++ b/packet_packer_test.go
@@ -37,19 +37,23 @@ var _ = Describe("Packet packer", func() {
 		ExpectWithOffset(0, extHdr.Length).To(BeEquivalentTo(r.Len() + int(extHdr.PacketNumberLen)))
 	}
 
+	appendFrames := func(fs, frames []wire.Frame) ([]wire.Frame, protocol.ByteCount) {
+		var length protocol.ByteCount
+		for _, f := range frames {
+			length += f.Length(packer.version)
+		}
+		return append(fs, frames...), length
+	}
+
 	expectAppendStreamFrames := func(frames ...wire.Frame) {
-		framer.EXPECT().AppendStreamFrames(gomock.Any(), gomock.Any()).DoAndReturn(func(fs []wire.Frame, _ protocol.ByteCount) []wire.Frame {
-			return append(fs, frames...)
+		framer.EXPECT().AppendStreamFrames(gomock.Any(), gomock.Any()).DoAndReturn(func(fs []wire.Frame, _ protocol.ByteCount) ([]wire.Frame, protocol.ByteCount) {
+			return appendFrames(fs, frames)
 		})
 	}
 
 	expectAppendControlFrames := func(frames ...wire.Frame) {
 		framer.EXPECT().AppendControlFrames(gomock.Any(), gomock.Any()).DoAndReturn(func(fs []wire.Frame, _ protocol.ByteCount) ([]wire.Frame, protocol.ByteCount) {
-			var length protocol.ByteCount
-			for _, f := range frames {
-				length += f.Length(packer.version)
-			}
-			return append(fs, frames...), length
+			return appendFrames(fs, frames)
 		})
 	}
 
@@ -311,9 +315,9 @@ var _ = Describe("Packet packer", func() {
 						maxSize = maxLen
 						return fs, 444
 					}),
-					framer.EXPECT().AppendStreamFrames(gomock.Any(), gomock.Any()).Do(func(_ []wire.Frame, maxLen protocol.ByteCount) []wire.Frame {
+					framer.EXPECT().AppendStreamFrames(gomock.Any(), gomock.Any()).Do(func(fs []wire.Frame, maxLen protocol.ByteCount) ([]wire.Frame, protocol.ByteCount) {
 						Expect(maxLen).To(Equal(maxSize - 444 + 1 /* data length of the STREAM frame */))
-						return nil
+						return fs, 0
 					}),
 				)
 				_, err := packer.PackPacket()
@@ -803,7 +807,7 @@ var _ = Describe("Packet packer", func() {
 				initialStream.EXPECT().HasData()
 				handshakeStream.EXPECT().HasData()
 				framer.EXPECT().AppendControlFrames(gomock.Any(), gomock.Any())
-				framer.EXPECT().AppendStreamFrames(gomock.Any(), gomock.Any()).Return([]wire.Frame{f})
+				framer.EXPECT().AppendStreamFrames(gomock.Any(), gomock.Any()).Return([]wire.Frame{f}, f.Length(packer.version))
 				packet, err := packer.PackPacket()
 				Expect(err).ToNot(HaveOccurred())
 				// cut off the tag that the mock sealer added