diff --git a/internal/wire/header.go b/internal/wire/header.go
index c4c6e8139..1bc1897e5 100644
--- a/internal/wire/header.go
+++ b/internal/wire/header.go
@@ -33,6 +33,7 @@ type Header struct {
 	Type         protocol.PacketType
 	IsLongHeader bool
 	KeyPhase     int
+	PayloadLen   protocol.ByteCount
 
 	// only needed for logging
 	isPublicHeader bool
diff --git a/internal/wire/ietf_header.go b/internal/wire/ietf_header.go
index c7938b845..87aafa66c 100644
--- a/internal/wire/ietf_header.go
+++ b/internal/wire/ietf_header.go
@@ -70,6 +70,11 @@ func parseLongHeader(b *bytes.Reader, sentBy protocol.Perspective, typeByte byte
 		return h, nil
 	}
 
+	pl, err := utils.ReadVarInt(b)
+	if err != nil {
+		return nil, err
+	}
+	h.PayloadLen = protocol.ByteCount(pl)
 	pn, err := utils.BigEndian.ReadUint32(b)
 	if err != nil {
 		return nil, err
@@ -143,6 +148,7 @@ func (h *Header) writeLongHeader(b *bytes.Buffer) error {
 	b.WriteByte(connIDLen)
 	b.Write(h.DestConnectionID.Bytes())
 	b.Write(h.SrcConnectionID.Bytes())
+	utils.WriteVarInt(b, uint64(h.PayloadLen))
 	utils.BigEndian.WriteUint32(b, uint32(h.PacketNumber))
 	return nil
 }
@@ -173,10 +179,9 @@ func (h *Header) writeShortHeader(b *bytes.Buffer) error {
 	return nil
 }
 
-// getHeaderLength gets the length of the Header in bytes.
 func (h *Header) getHeaderLength() (protocol.ByteCount, error) {
 	if h.IsLongHeader {
-		return 1 /* type byte */ + 4 /* version */ + 1 /* conn id len byte */ + protocol.ByteCount(h.DestConnectionID.Len()+h.SrcConnectionID.Len()) + 4 /* packet number */, nil
+		return 1 /* type byte */ + 4 /* version */ + 1 /* conn id len byte */ + protocol.ByteCount(h.DestConnectionID.Len()+h.SrcConnectionID.Len()) + utils.VarIntLen(uint64(h.PayloadLen)) + 4 /* packet number */, nil
 	}
 
 	length := protocol.ByteCount(1 /* type byte */ + h.DestConnectionID.Len())
@@ -192,7 +197,7 @@ func (h *Header) logHeader(logger utils.Logger) {
 		if h.Version == 0 {
 			logger.Debugf("    VersionNegotiationPacket{DestConnectionID: %s, SrcConnectionID: %s, SupportedVersions: %s}", h.DestConnectionID, h.SrcConnectionID, h.SupportedVersions)
 		} else {
-			logger.Debugf("   Long Header{Type: %s, DestConnectionID: %s, SrcConnectionID: %s, PacketNumber: %#x, Version: %s}", h.Type, h.DestConnectionID, h.SrcConnectionID, h.PacketNumber, h.Version)
+			logger.Debugf("   Long Header{Type: %s, DestConnectionID: %s, SrcConnectionID: %s, PacketNumber: %#x, PayloadLen: %d, Version: %s}", h.Type, h.DestConnectionID, h.SrcConnectionID, h.PacketNumber, h.PayloadLen, h.Version)
 		}
 	} else {
 		logger.Debugf("   Short Header{DestConnectionID: %s, PacketNumber: %#x, PacketNumberLen: %d, KeyPhase: %d}", h.DestConnectionID, h.PacketNumber, h.PacketNumberLen, h.KeyPhase)
diff --git a/internal/wire/ietf_header_test.go b/internal/wire/ietf_header_test.go
index e86593e57..2d6c25bae 100644
--- a/internal/wire/ietf_header_test.go
+++ b/internal/wire/ietf_header_test.go
@@ -59,15 +59,21 @@ var _ = Describe("IETF QUIC Header", func() {
 		})
 
 		Context("long headers", func() {
-			It("parses a long header", func() {
-				b := bytes.NewReader([]byte{
-					0x80 ^ uint8(protocol.PacketTypeInitial),
+			generatePacket := func(t protocol.PacketType) []byte {
+				data := []byte{
+					0x80 ^ uint8(t),
 					0x1, 0x2, 0x3, 0x4, // version number
 					0x55,                                           // connection ID lengths
 					0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe, 0x13, 0x37, // destination connection ID
 					0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe, 0x13, 0x37, // source connection ID
-					0xde, 0xca, 0xfb, 0xad, // packet number
-				})
+				}
+				data = append(data, encodeVarInt(0x1337)...)           // payload length
+				data = append(data, []byte{0xde, 0xca, 0xfb, 0xad}...) // packet number
+				return data
+			}
+
+			It("parses a long header", func() {
+				b := bytes.NewReader(generatePacket(protocol.PacketTypeInitial))
 				h, err := parseHeader(b, protocol.PerspectiveClient)
 				Expect(err).ToNot(HaveOccurred())
 				Expect(h.Type).To(Equal(protocol.PacketTypeInitial))
@@ -75,6 +81,7 @@ var _ = Describe("IETF QUIC Header", func() {
 				Expect(h.OmitConnectionID).To(BeFalse())
 				Expect(h.DestConnectionID).To(Equal(protocol.ConnectionID{0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe, 0x13, 0x37}))
 				Expect(h.SrcConnectionID).To(Equal(protocol.ConnectionID{0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe, 0x13, 0x37}))
+				Expect(h.PayloadLen).To(Equal(protocol.ByteCount(0x1337)))
 				Expect(h.PacketNumber).To(Equal(protocol.PacketNumber(0xdecafbad)))
 				Expect(h.PacketNumberLen).To(Equal(protocol.PacketNumberLen4))
 				Expect(h.Version).To(Equal(protocol.VersionNumber(0x1020304)))
@@ -83,13 +90,15 @@ var _ = Describe("IETF QUIC Header", func() {
 			})
 
 			It("parses a long header without a destination connection ID", func() {
-				b := bytes.NewReader([]byte{
+				data := []byte{
 					0x80 ^ uint8(protocol.PacketTypeInitial),
 					0x1, 0x2, 0x3, 0x4, // version number
 					0x01,                   // connection ID lengths
 					0xde, 0xad, 0xbe, 0xef, // source connection ID
-					0xde, 0xca, 0xfb, 0xad, // packet number
-				})
+				}
+				data = append(data, encodeVarInt(0x42)...) // payload length
+				data = append(data, []byte{0xde, 0xca, 0xfb, 0xad}...)
+				b := bytes.NewReader(data)
 				h, err := parseHeader(b, protocol.PerspectiveClient)
 				Expect(err).ToNot(HaveOccurred())
 				Expect(h.SrcConnectionID).To(Equal(protocol.ConnectionID{0xde, 0xad, 0xbe, 0xef}))
@@ -97,13 +106,15 @@ var _ = Describe("IETF QUIC Header", func() {
 			})
 
 			It("parses a long header without a source connection ID", func() {
-				b := bytes.NewReader([]byte{
+				data := []byte{
 					0x80 ^ uint8(protocol.PacketTypeInitial),
 					0x1, 0x2, 0x3, 0x4, // version number
 					0x70,                          // connection ID lengths
 					1, 2, 3, 4, 5, 6, 7, 8, 9, 10, // source connection ID
-					0xde, 0xca, 0xfb, 0xad, // packet number
-				})
+				}
+				data = append(data, encodeVarInt(0x42)...) // payload length
+				data = append(data, []byte{0xde, 0xca, 0xfb, 0xad}...)
+				b := bytes.NewReader(data)
 				h, err := parseHeader(b, protocol.PerspectiveClient)
 				Expect(err).ToNot(HaveOccurred())
 				Expect(h.SrcConnectionID).To(BeEmpty())
@@ -293,18 +304,21 @@ var _ = Describe("IETF QUIC Header", func() {
 					Type:             0x5,
 					DestConnectionID: protocol.ConnectionID{0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe},
 					SrcConnectionID:  protocol.ConnectionID{0xde, 0xca, 0xfb, 0xad, 0x0, 0x0, 0x13, 0x37},
+					PayloadLen:       0xcafe,
 					PacketNumber:     0xdecafbad,
 					Version:          0x1020304,
 				}).writeHeader(buf)
 				Expect(err).ToNot(HaveOccurred())
-				Expect(buf.Bytes()).To(Equal([]byte{
+				expected := []byte{
 					0x80 ^ 0x5,
 					0x1, 0x2, 0x3, 0x4, // version number
 					0x35,                               // connection ID lengths
-					0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe, // destination connection ID
+					0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe, // dest connection ID
 					0xde, 0xca, 0xfb, 0xad, 0x0, 0x0, 0x13, 0x37, // source connection ID
-					0xde, 0xca, 0xfb, 0xad, // packet number
-				}))
+				}
+				expected = append(expected, encodeVarInt(0xcafe)...)           // payload length
+				expected = append(expected, []byte{0xde, 0xca, 0xfb, 0xad}...) // packet number
+				Expect(buf.Bytes()).To(Equal(expected))
 			})
 
 			It("refuses to write a header with a too short connection ID", func() {
@@ -430,20 +444,35 @@ var _ = Describe("IETF QUIC Header", func() {
 			buf = &bytes.Buffer{}
 		})
 
-		It("has the right length for the long header", func() {
+		It("has the right length for the long header, for a short payload length", func() {
 			h := &Header{
 				IsLongHeader:     true,
+				PayloadLen:       1,
 				DestConnectionID: protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8},
 				SrcConnectionID:  protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8},
 			}
-			expectedLen := 1 /* type byte */ + 4 /* version */ + 1 /* conn ID len */ + 8 /* dest conn id */ + 8 /* src conn id */ + 4 /* packet number */
+			expectedLen := 1 /* type byte */ + 4 /* version */ + 1 /* conn ID len */ + 8 /* dest conn id */ + 8 /* src conn id */ + 1 /* short payload len */ + 4 /* packet number */
 			Expect(h.getHeaderLength()).To(BeEquivalentTo(expectedLen))
 			err := h.writeHeader(buf)
 			Expect(err).ToNot(HaveOccurred())
 			Expect(buf.Len()).To(Equal(expectedLen))
 		})
 
-		It("has the right length for a short header containing a connection ID", func() {
+		It("has the right length for the long header, for a long payload length", func() {
+			h := &Header{
+				IsLongHeader:     true,
+				PayloadLen:       1500,
+				DestConnectionID: protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8},
+				SrcConnectionID:  protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8},
+			}
+			expectedLen := 1 /* type byte */ + 4 /* version */ + 1 /* conn ID len */ + 8 /* dest conn id */ + 8 /* src conn id */ + 2 /* long payload len */ + 4 /* packet number */
+			Expect(h.getHeaderLength()).To(BeEquivalentTo(expectedLen))
+			err := h.writeHeader(buf)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(buf.Len()).To(Equal(expectedLen))
+		})
+
+		It("has the right length for a hort header containing a connection ID", func() {
 			h := &Header{
 				PacketNumberLen:  protocol.PacketNumberLen1,
 				DestConnectionID: protocol.ConnectionID{1, 2, 3, 4, 5, 6, 7, 8},
@@ -529,11 +558,12 @@ var _ = Describe("IETF QUIC Header", func() {
 				IsLongHeader:     true,
 				Type:             protocol.PacketTypeHandshake,
 				PacketNumber:     0x1337,
+				PayloadLen:       54321,
 				DestConnectionID: protocol.ConnectionID{0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe, 0x13, 0x37},
 				SrcConnectionID:  protocol.ConnectionID{0xde, 0xca, 0xfb, 0xad, 0x013, 0x37, 0x13, 0x37},
 				Version:          0xfeed,
 			}).logHeader(logger)
-			Expect(buf.String()).To(ContainSubstring("Long Header{Type: Handshake, DestConnectionID: 0xdeadbeefcafe1337, SrcConnectionID: 0xdecafbad13371337, PacketNumber: 0x1337, Version: 0xfeed}"))
+			Expect(buf.String()).To(ContainSubstring("Long Header{Type: Handshake, DestConnectionID: 0xdeadbeefcafe1337, SrcConnectionID: 0xdecafbad13371337, PacketNumber: 0x1337, PayloadLen: 54321, Version: 0xfeed}"))
 		})
 
 		It("logs Short Headers containing a connection ID", func() {