diff --git a/packet_packer.go b/packet_packer.go
index 7be70388..04668438 100644
--- a/packet_packer.go
+++ b/packet_packer.go
@@ -157,10 +157,22 @@ func (p *packetPacker) PackRetransmission(packet *ackhandler.Packet) ([]*packedP
 			frames = append(frames, frame)
 			controlFrames = controlFrames[1:]
 		}
+
+		// temporarily increase the maxFrameSize by the (minimum) length of the DataLen field
+		// this leads to a properly sized packet in all cases, since we do all the packet length calculations with StreamFrames that have the DataLen set
+		// however, for the last STREAM frame in the packet, we can omit the DataLen, thus yielding a packet of exactly the correct size
+		// for gQUIC STREAM frames, DataLen is always 2 bytes
+		// for IETF draft style STREAM frames, the length is encoded to either 1 or 2 bytes
+		if p.version.UsesIETFFrameFormat() {
+			maxSize++
+		} else {
+			maxSize += 2
+		}
 		for len(streamFrames) > 0 && payloadLength+protocol.MinStreamFrameSize < maxSize {
 			// TODO: optimize by setting DataLenPresent = false on all but the last STREAM frame
 			frame := streamFrames[0]
 			frameToAdd := frame
+
 			sf, err := frame.MaybeSplitOffFrame(maxSize-payloadLength, p.version)
 			if err != nil {
 				return nil, err
@@ -173,6 +185,9 @@ func (p *packetPacker) PackRetransmission(packet *ackhandler.Packet) ([]*packedP
 			payloadLength += frameToAdd.Length(p.version)
 			frames = append(frames, frameToAdd)
 		}
+		if sf, ok := frames[len(frames)-1].(*wire.StreamFrame); ok {
+			sf.DataLenPresent = false
+		}
 		raw, err := p.writeAndSealPacket(header, frames, sealer)
 		if err != nil {
 			return nil, err
@@ -351,7 +366,7 @@ func (p *packetPacker) composeNextPacket(
 
 	// temporarily increase the maxFrameSize by the (minimum) length of the DataLen field
 	// this leads to a properly sized packet in all cases, since we do all the packet length calculations with StreamFrames that have the DataLen set
-	// however, for the last StreamFrame in the packet, we can omit the DataLen, thus yielding a packet of exactly the correct size
+	// however, for the last STREAM frame in the packet, we can omit the DataLen, thus yielding a packet of exactly the correct size
 	// for gQUIC STREAM frames, DataLen is always 2 bytes
 	// for IETF draft style STREAM frames, the length is encoded to either 1 or 2 bytes
 	if p.version.UsesIETFFrameFormat() {
diff --git a/packet_packer_test.go b/packet_packer_test.go
index a85adeed..57ab1b26 100644
--- a/packet_packer_test.go
+++ b/packet_packer_test.go
@@ -809,8 +809,10 @@ var _ = Describe("Packet packer", func() {
 			sf2 := packets[1].frames[1].(*wire.StreamFrame)
 			Expect(sf1.StreamID).To(Equal(protocol.StreamID(42)))
 			Expect(sf1.Offset).To(Equal(protocol.ByteCount(1337)))
+			Expect(sf1.DataLenPresent).To(BeFalse())
 			Expect(sf2.StreamID).To(Equal(protocol.StreamID(42)))
 			Expect(sf2.Offset).To(Equal(protocol.ByteCount(1337) + sf1.DataLen()))
+			Expect(sf2.DataLenPresent).To(BeFalse())
 			Expect(sf1.DataLen() + sf2.DataLen()).To(Equal(protocol.MaxPacketSize * 3 / 2))
 			Expect(packets[0].raw).To(HaveLen(int(protocol.MaxPacketSize)))
 		})
@@ -844,6 +846,29 @@ var _ = Describe("Packet packer", func() {
 			Expect(len(packets[0].raw) + int(packets[1].frames[1].Length(packer.version))).To(BeNumerically(">", protocol.MaxPacketSize-protocol.MinStreamFrameSize))
 		})
 
+		It("correctly sets the DataLenPresent on STREAM frames", func() {
+			frames := []wire.Frame{
+				&wire.StreamFrame{StreamID: 4, Data: []byte("foobar"), DataLenPresent: true},
+				&wire.StreamFrame{StreamID: 5, Data: []byte("barfoo")},
+			}
+			packets, err := packer.PackRetransmission(&ackhandler.Packet{
+				EncryptionLevel: protocol.EncryptionForwardSecure,
+				Frames:          frames,
+			})
+			Expect(err).ToNot(HaveOccurred())
+			Expect(packets).To(HaveLen(1))
+			p := packets[0]
+			Expect(p.frames).To(HaveLen(3))
+			Expect(p.frames[1]).To(BeAssignableToTypeOf(&wire.StreamFrame{}))
+			Expect(p.frames[2]).To(BeAssignableToTypeOf(&wire.StreamFrame{}))
+			sf1 := p.frames[1].(*wire.StreamFrame)
+			sf2 := p.frames[2].(*wire.StreamFrame)
+			Expect(sf1.StreamID).To(Equal(protocol.StreamID(4)))
+			Expect(sf1.DataLenPresent).To(BeTrue())
+			Expect(sf2.StreamID).To(Equal(protocol.StreamID(5)))
+			Expect(sf2.DataLenPresent).To(BeFalse())
+		})
+
 	})
 
 	Context("packing ACK packets", func() {