diff --git a/ackhandlerlegacy/sent_packet_handler.go b/ackhandlerlegacy/sent_packet_handler.go
index ccc5a9e1..c28409aa 100644
--- a/ackhandlerlegacy/sent_packet_handler.go
+++ b/ackhandlerlegacy/sent_packet_handler.go
@@ -106,8 +106,6 @@ func (h *sentPacketHandler) queuePacketForRetransmission(packet *Packet) {
 	h.bytesInFlight -= packet.Length
 	h.retransmissionQueue = append(h.retransmissionQueue, packet)
 	packet.Retransmitted = true
-
-	// TODO: delete from packetHistory once we drop support for version smaller than QUIC 33
 }
 
 func (h *sentPacketHandler) SentPacket(packet *Packet) error {
diff --git a/ackhandlerlegacy/sent_packet_handler_test.go b/ackhandlerlegacy/sent_packet_handler_test.go
index a0d644a3..50b6f9f1 100644
--- a/ackhandlerlegacy/sent_packet_handler_test.go
+++ b/ackhandlerlegacy/sent_packet_handler_test.go
@@ -459,6 +459,7 @@ var _ = Describe("SentPacketHandler", func() {
 				Expect(err).ToNot(HaveOccurred())
 			}
 			packet := handler.DequeuePacketForRetransmission()
+			Expect(packet).ToNot(BeNil())
 			Expect(packet.PacketNumber).To(Equal(protocol.PacketNumber(3)))
 			Expect(handler.DequeuePacketForRetransmission()).To(BeNil())
 		})
@@ -473,6 +474,7 @@ var _ = Describe("SentPacketHandler", func() {
 				Expect(err).ToNot(HaveOccurred())
 			}
 			packet := handler.DequeuePacketForRetransmission()
+			Expect(packet).ToNot(BeNil())
 			Expect(packet.PacketNumber).To(Equal(protocol.PacketNumber(2)))
 			packet = handler.DequeuePacketForRetransmission()
 			Expect(packet.PacketNumber).To(Equal(protocol.PacketNumber(4)))
@@ -491,8 +493,10 @@ var _ = Describe("SentPacketHandler", func() {
 				_, err := handler.nackPacket(4)
 				Expect(err).ToNot(HaveOccurred())
 			}
-			_ = handler.DequeuePacketForRetransmission()
-			_ = handler.DequeuePacketForRetransmission()
+			packet := handler.DequeuePacketForRetransmission()
+			Expect(packet).ToNot(BeNil())
+			packet = handler.DequeuePacketForRetransmission()
+			Expect(packet).ToNot(BeNil())
 			Expect(handler.DequeuePacketForRetransmission()).To(BeNil())
 		})
 
@@ -508,7 +512,7 @@ var _ = Describe("SentPacketHandler", func() {
 			Expect(handler.highestInOrderAckedPacketNumber).To(Equal(protocol.PacketNumber(2)))
 		})
 
-		It("does not retransmit a packet if a belated was received", func() {
+		It("does not retransmit a packet if a belated ACK was received", func() {
 			// lose packet by NACKing it often enough
 			for i := uint8(0); i < protocol.RetransmissionThreshold+1; i++ {
 				_, err := handler.nackPacket(2)
diff --git a/ackhandlernew/sent_packet_handler.go b/ackhandlernew/sent_packet_handler.go
index aceeb9e3..4adf9715 100644
--- a/ackhandlernew/sent_packet_handler.go
+++ b/ackhandlernew/sent_packet_handler.go
@@ -85,14 +85,10 @@ func (h *sentPacketHandler) ackPacket(packetNumber protocol.PacketNumber) *Packe
 
 func (h *sentPacketHandler) nackPacket(packetNumber protocol.PacketNumber) (*Packet, error) {
 	packet, ok := h.packetHistory[packetNumber]
-	if !ok {
-		return nil, ErrMapAccess
-	}
-
-	// If the packet has already been retransmitted, do nothing.
+	// This means that the packet has already been retransmitted, do nothing.
 	// We're probably only receiving another NACK for this packet because the
 	// retransmission has not yet arrived at the client.
-	if packet.Retransmitted {
+	if !ok {
 		return nil, nil
 	}
 
@@ -109,8 +105,6 @@ func (h *sentPacketHandler) queuePacketForRetransmission(packet *Packet) {
 	h.bytesInFlight -= packet.Length
 	h.retransmissionQueue = append(h.retransmissionQueue, packet)
 	packet.Retransmitted = true
-
-	// TODO: delete from packetHistory once we drop support for version smaller than QUIC 33
 }
 
 func (h *sentPacketHandler) SentPacket(packet *Packet) error {
@@ -231,12 +225,14 @@ func (h *sentPacketHandler) DequeuePacketForRetransmission() (packet *Packet) {
 		packet = h.retransmissionQueue[queueLen-1]
 		h.retransmissionQueue = h.retransmissionQueue[:queueLen-1]
 
-		// check if the packet was ACKed after it was already queued for retransmission
-		// if so, it doesn't exist in the packetHistory anymore. Skip it then
+		// this happens if a belated ACK arrives for this packet
+		// no need to retransmit it
 		_, ok := h.packetHistory[packet.PacketNumber]
 		if !ok {
 			continue
 		}
+
+		delete(h.packetHistory, packet.PacketNumber)
 		return packet
 	}
 
diff --git a/ackhandlernew/sent_packet_handler_test.go b/ackhandlernew/sent_packet_handler_test.go
index 2fe800af..50bfee3f 100644
--- a/ackhandlernew/sent_packet_handler_test.go
+++ b/ackhandlernew/sent_packet_handler_test.go
@@ -390,10 +390,21 @@ var _ = Describe("SentPacketHandler", func() {
 				Expect(err).ToNot(HaveOccurred())
 			}
 			packet := handler.DequeuePacketForRetransmission()
+			Expect(packet).ToNot(BeNil())
 			Expect(packet.PacketNumber).To(Equal(protocol.PacketNumber(3)))
 			Expect(handler.DequeuePacketForRetransmission()).To(BeNil())
 		})
 
+		It("deletes a packet from the packetHistory map when sending out the retransmission", func() {
+			for i := uint8(0); i < protocol.RetransmissionThreshold+1; i++ {
+				_, err := handler.nackPacket(3)
+				Expect(err).ToNot(HaveOccurred())
+			}
+			packet := handler.DequeuePacketForRetransmission()
+			Expect(packet).ToNot(BeNil())
+			Expect(handler.packetHistory).ToNot(HaveKey(protocol.PacketNumber(3)))
+		})
+
 		It("keeps the packets in the right order", func() {
 			for i := uint8(0); i < protocol.RetransmissionThreshold+1; i++ {
 				_, err := handler.nackPacket(4)
@@ -404,8 +415,10 @@ var _ = Describe("SentPacketHandler", func() {
 				Expect(err).ToNot(HaveOccurred())
 			}
 			packet := handler.DequeuePacketForRetransmission()
+			Expect(packet).ToNot(BeNil())
 			Expect(packet.PacketNumber).To(Equal(protocol.PacketNumber(2)))
 			packet = handler.DequeuePacketForRetransmission()
+			Expect(packet).ToNot(BeNil())
 			Expect(packet.PacketNumber).To(Equal(protocol.PacketNumber(4)))
 		})
 
@@ -422,8 +435,10 @@ var _ = Describe("SentPacketHandler", func() {
 				_, err := handler.nackPacket(4)
 				Expect(err).ToNot(HaveOccurred())
 			}
-			_ = handler.DequeuePacketForRetransmission()
-			_ = handler.DequeuePacketForRetransmission()
+			packet := handler.DequeuePacketForRetransmission()
+			Expect(packet).ToNot(BeNil())
+			packet = handler.DequeuePacketForRetransmission()
+			Expect(packet).ToNot(BeNil())
 			Expect(handler.DequeuePacketForRetransmission()).To(BeNil())
 		})
 
@@ -443,7 +458,7 @@ var _ = Describe("SentPacketHandler", func() {
 			Expect(handler.highestInOrderAckedPacketNumber).To(Equal(protocol.PacketNumber(2)))
 		})
 
-		It("does not retransmit a packet if a belated was received", func() {
+		It("does not retransmit a packet if a belated ACK was received", func() {
 			// lose packet by NACKing it often enough
 			for i := uint8(0); i < protocol.RetransmissionThreshold+1; i++ {
 				_, err := handler.nackPacket(2)