diff --git a/ackhandler/sent_packet_handler.go b/ackhandler/sent_packet_handler.go
index c21ad189..10b8c828 100644
--- a/ackhandler/sent_packet_handler.go
+++ b/ackhandler/sent_packet_handler.go
@@ -25,8 +25,10 @@ var errPacketNumberNotIncreasing = errors.New("Already sent a packet with a high
 type sentPacketHandler struct {
 	lastSentPacketNumber protocol.PacketNumber
 	lastSentPacketTime   time.Time
-	LargestInOrderAcked  protocol.PacketNumber
-	LargestAcked         protocol.PacketNumber
+	skippedPackets       []protocol.PacketNumber
+
+	LargestInOrderAcked protocol.PacketNumber
+	LargestAcked        protocol.PacketNumber
 
 	largestReceivedPacketWithAck protocol.PacketNumber
 
@@ -121,6 +123,10 @@ func (h *sentPacketHandler) SentPacket(packet *ackhandlerlegacy.Packet) error {
 		return errPacketNumberNotIncreasing
 	}
 
+	for p := h.lastSentPacketNumber + 1; p < packet.PacketNumber; p++ {
+		h.skippedPackets = append(h.skippedPackets, p)
+	}
+
 	now := time.Now()
 	h.lastSentPacketTime = now
 	packet.SendTime = now
diff --git a/ackhandler/sent_packet_handler_test.go b/ackhandler/sent_packet_handler_test.go
index d5f52eb5..df3a7b27 100644
--- a/ackhandler/sent_packet_handler_test.go
+++ b/ackhandler/sent_packet_handler_test.go
@@ -91,6 +91,7 @@ var _ = Describe("SentPacketHandler", func() {
 			Expect(handler.packetHistory.Front().Value.PacketNumber).To(Equal(protocol.PacketNumber(1)))
 			Expect(handler.packetHistory.Back().Value.PacketNumber).To(Equal(protocol.PacketNumber(2)))
 			Expect(handler.BytesInFlight()).To(Equal(protocol.ByteCount(3)))
+			Expect(handler.skippedPackets).To(BeEmpty())
 		})
 
 		It("rejects packets with the same packet number", func() {
@@ -103,6 +104,7 @@ var _ = Describe("SentPacketHandler", func() {
 			Expect(handler.lastSentPacketNumber).To(Equal(protocol.PacketNumber(1)))
 			Expect(handler.packetHistory.Front().Value.PacketNumber).To(Equal(protocol.PacketNumber(1)))
 			Expect(handler.BytesInFlight()).To(Equal(protocol.ByteCount(1)))
+			Expect(handler.skippedPackets).To(BeEmpty())
 		})
 
 		It("rejects packets with decreasing packet number", func() {
@@ -117,21 +119,6 @@ var _ = Describe("SentPacketHandler", func() {
 			Expect(handler.BytesInFlight()).To(Equal(protocol.ByteCount(1)))
 		})
 
-		It("works with non-consecutive packet numbers", func() {
-			packet1 := ackhandlerlegacy.Packet{PacketNumber: 1, Frames: []frames.Frame{&streamFrame}, Length: 1}
-			packet2 := ackhandlerlegacy.Packet{PacketNumber: 3, Frames: []frames.Frame{&streamFrame}, Length: 2}
-			err := handler.SentPacket(&packet1)
-			Expect(err).ToNot(HaveOccurred())
-			err = handler.SentPacket(&packet2)
-			Expect(err).ToNot(HaveOccurred())
-			Expect(handler.lastSentPacketNumber).To(Equal(protocol.PacketNumber(3)))
-			el := handler.packetHistory.Front()
-			Expect(el.Value.PacketNumber).To(Equal(protocol.PacketNumber(1)))
-			el = el.Next()
-			Expect(el.Value.PacketNumber).To(Equal(protocol.PacketNumber(3)))
-			Expect(handler.BytesInFlight()).To(Equal(protocol.ByteCount(3)))
-		})
-
 		It("stores the sent time", func() {
 			packet := ackhandlerlegacy.Packet{PacketNumber: 1, Frames: []frames.Frame{&streamFrame}, Length: 1}
 			err := handler.SentPacket(&packet)
@@ -145,6 +132,50 @@ var _ = Describe("SentPacketHandler", func() {
 			Expect(err).ToNot(HaveOccurred())
 			Expect(handler.lastSentPacketTime.Unix()).To(BeNumerically("~", time.Now().Unix(), 1))
 		})
+
+		Context("skipped packet numbers", func() {
+			It("works with non-consecutive packet numbers", func() {
+				packet1 := ackhandlerlegacy.Packet{PacketNumber: 1, Frames: []frames.Frame{&streamFrame}, Length: 1}
+				packet2 := ackhandlerlegacy.Packet{PacketNumber: 3, Frames: []frames.Frame{&streamFrame}, Length: 2}
+				err := handler.SentPacket(&packet1)
+				Expect(err).ToNot(HaveOccurred())
+				err = handler.SentPacket(&packet2)
+				Expect(err).ToNot(HaveOccurred())
+				Expect(handler.lastSentPacketNumber).To(Equal(protocol.PacketNumber(3)))
+				el := handler.packetHistory.Front()
+				Expect(el.Value.PacketNumber).To(Equal(protocol.PacketNumber(1)))
+				el = el.Next()
+				Expect(el.Value.PacketNumber).To(Equal(protocol.PacketNumber(3)))
+				Expect(handler.BytesInFlight()).To(Equal(protocol.ByteCount(3)))
+				Expect(handler.skippedPackets).To(HaveLen(1))
+				Expect(handler.skippedPackets[0]).To(Equal(protocol.PacketNumber(2)))
+			})
+
+			It("recognizes multiple skipped packets", func() {
+				packet1 := ackhandlerlegacy.Packet{PacketNumber: 1, Frames: []frames.Frame{&streamFrame}, Length: 1}
+				packet2 := ackhandlerlegacy.Packet{PacketNumber: 3, Frames: []frames.Frame{&streamFrame}, Length: 2}
+				packet3 := ackhandlerlegacy.Packet{PacketNumber: 5, Frames: []frames.Frame{&streamFrame}, Length: 2}
+				err := handler.SentPacket(&packet1)
+				Expect(err).ToNot(HaveOccurred())
+				err = handler.SentPacket(&packet2)
+				Expect(err).ToNot(HaveOccurred())
+				err = handler.SentPacket(&packet3)
+				Expect(err).ToNot(HaveOccurred())
+				Expect(handler.skippedPackets).To(HaveLen(2))
+				Expect(handler.skippedPackets).To(Equal([]protocol.PacketNumber{2, 4}))
+			})
+
+			It("recognizes multiple consecutive skipped packets", func() {
+				packet1 := ackhandlerlegacy.Packet{PacketNumber: 1, Frames: []frames.Frame{&streamFrame}, Length: 1}
+				packet2 := ackhandlerlegacy.Packet{PacketNumber: 4, Frames: []frames.Frame{&streamFrame}, Length: 2}
+				err := handler.SentPacket(&packet1)
+				Expect(err).ToNot(HaveOccurred())
+				err = handler.SentPacket(&packet2)
+				Expect(err).ToNot(HaveOccurred())
+				Expect(handler.skippedPackets).To(HaveLen(2))
+				Expect(handler.skippedPackets).To(Equal([]protocol.PacketNumber{2, 3}))
+			})
+		})
 	})
 
 	Context("DOS mitigation", func() {