diff --git a/go.mod b/go.mod
index 78fb85ae..4de19ee0 100644
--- a/go.mod
+++ b/go.mod
@@ -9,7 +9,7 @@ require (
 	github.com/golang/protobuf v1.3.0
 	github.com/marten-seemann/chacha20 v0.2.0
 	github.com/marten-seemann/qpack v0.1.0
-	github.com/marten-seemann/qtls v0.4.1
+	github.com/marten-seemann/qtls v0.5.0
 	github.com/onsi/ginkgo v1.7.0
 	github.com/onsi/gomega v1.4.3
 	golang.org/x/crypto v0.0.0-20190829043050-9756ffdc2472
diff --git a/go.sum b/go.sum
index a0157b15..eea70312 100644
--- a/go.sum
+++ b/go.sum
@@ -15,8 +15,8 @@ github.com/marten-seemann/chacha20 v0.2.0 h1:f40vqzzx+3GdOmzQoItkLX5WLvHgPgyYqFF
 github.com/marten-seemann/chacha20 v0.2.0/go.mod h1:HSdjFau7GzYRj+ahFNwsO3ouVJr1HFkWoEwNDb4TMtE=
 github.com/marten-seemann/qpack v0.1.0 h1:/0M7lkda/6mus9B8u34Asqm8ZhHAAt9Ho0vniNuVSVg=
 github.com/marten-seemann/qpack v0.1.0/go.mod h1:LFt1NU/Ptjip0C2CPkhimBz5CGE3WGDAUWqna+CNTrI=
-github.com/marten-seemann/qtls v0.4.1 h1:YlT8QP3WCCvvok7MGEZkMldXbyqgr8oFg5/n8Gtbkks=
-github.com/marten-seemann/qtls v0.4.1/go.mod h1:pxVXcHHw1pNIt8Qo0pwSYQEoZ8yYOOPXTCZLQQunvRc=
+github.com/marten-seemann/qtls v0.5.0 h1:psje4bHl6372lku0pTIt2PZ9HcVJyBIuW9pZn+u2vhY=
+github.com/marten-seemann/qtls v0.5.0/go.mod h1:pxVXcHHw1pNIt8Qo0pwSYQEoZ8yYOOPXTCZLQQunvRc=
 github.com/onsi/ginkgo v1.6.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
 github.com/onsi/ginkgo v1.7.0 h1:WSHQ+IS43OoUrWtD1/bbclrwK8TTH5hzp+umCiuxHgs=
 github.com/onsi/ginkgo v1.7.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
@@ -34,6 +34,7 @@ golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f h1:wMNYb4v58l5UBM7MYRLPG6Zh
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180909124046-d0be0721c37e/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d h1:+R4KGOnez64A81RvjARKc4UT5/tI9ujCIVX+P5KiHuI=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190904154756-749cb33beabd h1:DBH9mDw0zluJT/R+nGuV3jWFWLFaHyYZWD4tOT+cjn0=
 golang.org/x/sys v0.0.0-20190904154756-749cb33beabd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
diff --git a/internal/handshake/crypto_setup.go b/internal/handshake/crypto_setup.go
index 9c28683e..48dc8f34 100644
--- a/internal/handshake/crypto_setup.go
+++ b/internal/handshake/crypto_setup.go
@@ -66,6 +66,7 @@ type cryptoSetup struct {
 
 	messageChan chan []byte
 
+	ourParams  *TransportParameters
 	paramsChan <-chan []byte
 
 	runner handshakeRunner
@@ -124,6 +125,7 @@ func NewCryptoSetupClient(
 	tp *TransportParameters,
 	runner handshakeRunner,
 	tlsConf *tls.Config,
+	enable0RTT bool,
 	rttStats *congestion.RTTStats,
 	logger utils.Logger,
 ) (CryptoSetup, <-chan struct{} /* ClientHello written */) {
@@ -135,6 +137,7 @@ func NewCryptoSetupClient(
 		tp,
 		runner,
 		tlsConf,
+		enable0RTT,
 		rttStats,
 		logger,
 		protocol.PerspectiveClient,
@@ -153,6 +156,7 @@ func NewCryptoSetupServer(
 	tp *TransportParameters,
 	runner handshakeRunner,
 	tlsConf *tls.Config,
+	enable0RTT bool,
 	rttStats *congestion.RTTStats,
 	logger utils.Logger,
 ) CryptoSetup {
@@ -164,6 +168,7 @@ func NewCryptoSetupServer(
 		tp,
 		runner,
 		tlsConf,
+		enable0RTT,
 		rttStats,
 		logger,
 		protocol.PerspectiveServer,
@@ -180,6 +185,7 @@ func newCryptoSetup(
 	tp *TransportParameters,
 	runner handshakeRunner,
 	tlsConf *tls.Config,
+	enable0RTT bool,
 	rttStats *congestion.RTTStats,
 	logger utils.Logger,
 	perspective protocol.Perspective,
@@ -196,6 +202,7 @@ func newCryptoSetup(
 		readEncLevel:           protocol.EncryptionInitial,
 		writeEncLevel:          protocol.EncryptionInitial,
 		runner:                 runner,
+		ourParams:              tp,
 		paramsChan:             extHandler.TransportParameters(),
 		logger:                 logger,
 		perspective:            perspective,
@@ -208,7 +215,7 @@ func newCryptoSetup(
 		writeRecord:            make(chan struct{}, 1),
 		closeChan:              make(chan struct{}),
 	}
-	qtlsConf := tlsConfigToQtlsConfig(tlsConf, cs, extHandler)
+	qtlsConf := tlsConfigToQtlsConfig(tlsConf, cs, extHandler, cs.accept0RTT, enable0RTT)
 	cs.tlsConf = qtlsConf
 	return cs, cs.clientHelloWrittenChan
 }
@@ -423,7 +430,7 @@ func (h *cryptoSetup) handleMessageForClient(msgType messageType) bool {
 
 // only valid for the server
 func (h *cryptoSetup) maybeSendSessionTicket() {
-	ticket, err := h.conn.GetSessionTicket()
+	ticket, err := h.conn.GetSessionTicket(h.ourParams.MarshalForSessionTicket())
 	if err != nil {
 		h.onError(alertInternalError, err.Error())
 		return
@@ -433,6 +440,10 @@ func (h *cryptoSetup) maybeSendSessionTicket() {
 	}
 }
 
+func (h *cryptoSetup) accept0RTT(sessionTicketData []byte) bool {
+	return h.ourParams.ValidFromSessionTicket(sessionTicketData)
+}
+
 func (h *cryptoSetup) handlePostHandshakeMessage() {
 	// make sure the handshake has already completed
 	<-h.handshakeDone
diff --git a/internal/handshake/crypto_setup_test.go b/internal/handshake/crypto_setup_test.go
index a870ac2b..20fa7385 100644
--- a/internal/handshake/crypto_setup_test.go
+++ b/internal/handshake/crypto_setup_test.go
@@ -95,6 +95,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 			&TransportParameters{},
 			NewMockHandshakeRunner(mockCtrl),
 			tlsConf,
+			false,
 			&congestion.RTTStats{},
 			utils.DefaultLogger.WithPrefix("server"),
 		)
@@ -126,6 +127,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 			&TransportParameters{},
 			runner,
 			testdata.GetTLSConfig(),
+			false,
 			&congestion.RTTStats{},
 			utils.DefaultLogger.WithPrefix("server"),
 		)
@@ -163,6 +165,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 			&TransportParameters{},
 			runner,
 			testdata.GetTLSConfig(),
+			false,
 			&congestion.RTTStats{},
 			utils.DefaultLogger.WithPrefix("server"),
 		)
@@ -203,6 +206,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 			&TransportParameters{},
 			runner,
 			serverConf,
+			false,
 			&congestion.RTTStats{},
 			utils.DefaultLogger.WithPrefix("server"),
 		)
@@ -236,6 +240,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 			&TransportParameters{},
 			NewMockHandshakeRunner(mockCtrl),
 			serverConf,
+			false,
 			&congestion.RTTStats{},
 			utils.DefaultLogger.WithPrefix("server"),
 		)
@@ -324,6 +329,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 				&TransportParameters{},
 				cRunner,
 				clientConf,
+				false,
 				&congestion.RTTStats{},
 				utils.DefaultLogger.WithPrefix("client"),
 			)
@@ -345,6 +351,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 				&TransportParameters{StatelessResetToken: &token},
 				sRunner,
 				serverConf,
+				false,
 				&congestion.RTTStats{},
 				utils.DefaultLogger.WithPrefix("server"),
 			)
@@ -397,6 +404,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 				&TransportParameters{},
 				runner,
 				&tls.Config{InsecureSkipVerify: true},
+				false,
 				&congestion.RTTStats{},
 				utils.DefaultLogger.WithPrefix("client"),
 			)
@@ -437,6 +445,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 				cTransportParameters,
 				cRunner,
 				clientConf,
+				false,
 				&congestion.RTTStats{},
 				utils.DefaultLogger.WithPrefix("client"),
 			)
@@ -459,6 +468,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 				sTransportParameters,
 				sRunner,
 				serverConf,
+				false,
 				&congestion.RTTStats{},
 				utils.DefaultLogger.WithPrefix("server"),
 			)
@@ -495,6 +505,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 					&TransportParameters{},
 					cRunner,
 					clientConf,
+					false,
 					&congestion.RTTStats{},
 					utils.DefaultLogger.WithPrefix("client"),
 				)
@@ -512,6 +523,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 					&TransportParameters{},
 					sRunner,
 					serverConf,
+					false,
 					&congestion.RTTStats{},
 					utils.DefaultLogger.WithPrefix("server"),
 				)
@@ -550,6 +562,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 					&TransportParameters{},
 					cRunner,
 					clientConf,
+					false,
 					&congestion.RTTStats{},
 					utils.DefaultLogger.WithPrefix("client"),
 				)
@@ -567,6 +580,7 @@ var _ = Describe("Crypto Setup TLS", func() {
 					&TransportParameters{},
 					sRunner,
 					serverConf,
+					false,
 					&congestion.RTTStats{},
 					utils.DefaultLogger.WithPrefix("server"),
 				)
diff --git a/internal/handshake/qtls.go b/internal/handshake/qtls.go
index 67ed90a6..9b8ec31f 100644
--- a/internal/handshake/qtls.go
+++ b/internal/handshake/qtls.go
@@ -70,6 +70,8 @@ func tlsConfigToQtlsConfig(
 	c *tls.Config,
 	recordLayer qtls.RecordLayer,
 	extHandler tlsExtensionHandler,
+	accept0RTT func([]byte) bool,
+	enable0RTT bool,
 ) *qtls.Config {
 	if c == nil {
 		c = &tls.Config{}
@@ -96,14 +98,14 @@ func tlsConfigToQtlsConfig(
 			if tlsConf == nil {
 				return nil, nil
 			}
-			return tlsConfigToQtlsConfig(tlsConf, recordLayer, extHandler), nil
+			return tlsConfigToQtlsConfig(tlsConf, recordLayer, extHandler, accept0RTT, enable0RTT), nil
 		}
 	}
 	var csc qtls.ClientSessionCache
 	if c.ClientSessionCache != nil {
 		csc = &clientSessionCache{c.ClientSessionCache}
 	}
-	return &qtls.Config{
+	conf := &qtls.Config{
 		Rand:                        c.Rand,
 		Time:                        c.Time,
 		Certificates:                c.Certificates,
@@ -133,7 +135,13 @@ func tlsConfigToQtlsConfig(
 		AlternativeRecordLayer: recordLayer,
 		GetExtensions:          extHandler.GetExtensions,
 		ReceivedExtensions:     extHandler.ReceivedExtensions,
+		Accept0RTT:             accept0RTT,
 	}
+	if enable0RTT {
+		conf.Enable0RTT = true
+		conf.MaxEarlyData = 0xffffffff
+	}
+	return conf
 }
 
 func cipherSuiteName(id uint16) string {
diff --git a/internal/handshake/qtls_test.go b/internal/handshake/qtls_test.go
index 481b407d..55ea1acf 100644
--- a/internal/handshake/qtls_test.go
+++ b/internal/handshake/qtls_test.go
@@ -28,19 +28,19 @@ func (*mockExtensionHandler) TransportParameters() <-chan []byte { panic("not im
 var _ = Describe("qtls.Config generation", func() {
 	It("sets MinVersion and MaxVersion", func() {
 		tlsConf := &tls.Config{MinVersion: tls.VersionTLS11, MaxVersion: tls.VersionTLS12}
-		qtlsConf := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{})
+		qtlsConf := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{}, nil, false)
 		Expect(qtlsConf.MinVersion).To(BeEquivalentTo(tls.VersionTLS13))
 		Expect(qtlsConf.MaxVersion).To(BeEquivalentTo(tls.VersionTLS13))
 	})
 
 	It("works when called with a nil config", func() {
-		qtlsConf := tlsConfigToQtlsConfig(nil, nil, &mockExtensionHandler{})
+		qtlsConf := tlsConfigToQtlsConfig(nil, nil, &mockExtensionHandler{}, nil, false)
 		Expect(qtlsConf).ToNot(BeNil())
 	})
 
 	It("sets the setter and getter function for TLS extensions", func() {
 		extHandler := &mockExtensionHandler{}
-		qtlsConf := tlsConfigToQtlsConfig(&tls.Config{}, nil, extHandler)
+		qtlsConf := tlsConfigToQtlsConfig(&tls.Config{}, nil, extHandler, nil, false)
 		Expect(extHandler.get).To(BeFalse())
 		qtlsConf.GetExtensions(10)
 		Expect(extHandler.get).To(BeTrue())
@@ -49,17 +49,33 @@ var _ = Describe("qtls.Config generation", func() {
 		Expect(extHandler.received).To(BeTrue())
 	})
 
+	It("sets the Accept0RTT callback", func() {
+		accept0RTT := func([]byte) bool { return true }
+		qtlsConf := tlsConfigToQtlsConfig(nil, nil, &mockExtensionHandler{}, accept0RTT, false)
+		Expect(qtlsConf.Accept0RTT).ToNot(BeNil())
+		Expect(qtlsConf.Accept0RTT(nil)).To(BeTrue())
+	})
+
+	It("enables 0-RTT", func() {
+		qtlsConf := tlsConfigToQtlsConfig(nil, nil, &mockExtensionHandler{}, nil, false)
+		Expect(qtlsConf.Enable0RTT).To(BeFalse())
+		Expect(qtlsConf.MaxEarlyData).To(BeZero())
+		qtlsConf = tlsConfigToQtlsConfig(nil, nil, &mockExtensionHandler{}, nil, true)
+		Expect(qtlsConf.Enable0RTT).To(BeTrue())
+		Expect(qtlsConf.MaxEarlyData).To(Equal(uint32(0xffffffff)))
+	})
+
 	It("initializes such that the session ticket key remains constant", func() {
 		tlsConf := &tls.Config{}
-		qtlsConf1 := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{})
-		qtlsConf2 := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{})
+		qtlsConf1 := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{}, nil, false)
+		qtlsConf2 := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{}, nil, false)
 		Expect(qtlsConf1.SessionTicketKey).ToNot(BeZero()) // should now contain a random value
 		Expect(qtlsConf1.SessionTicketKey).To(Equal(qtlsConf2.SessionTicketKey))
 	})
 
 	Context("GetConfigForClient callback", func() {
 		It("doesn't set it if absent", func() {
-			qtlsConf := tlsConfigToQtlsConfig(&tls.Config{}, nil, &mockExtensionHandler{})
+			qtlsConf := tlsConfigToQtlsConfig(&tls.Config{}, nil, &mockExtensionHandler{}, nil, false)
 			Expect(qtlsConf.GetConfigForClient).To(BeNil())
 		})
 
@@ -70,7 +86,7 @@ var _ = Describe("qtls.Config generation", func() {
 				},
 			}
 			extHandler := &mockExtensionHandler{}
-			qtlsConf := tlsConfigToQtlsConfig(tlsConf, nil, extHandler)
+			qtlsConf := tlsConfigToQtlsConfig(tlsConf, nil, extHandler, nil, false)
 			Expect(qtlsConf.GetConfigForClient).ToNot(BeNil())
 			confForClient, err := qtlsConf.GetConfigForClient(nil)
 			Expect(err).ToNot(HaveOccurred())
@@ -90,7 +106,7 @@ var _ = Describe("qtls.Config generation", func() {
 					return nil, testErr
 				},
 			}
-			qtlsConf := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{})
+			qtlsConf := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{}, nil, false)
 			_, err := qtlsConf.GetConfigForClient(nil)
 			Expect(err).To(MatchError(testErr))
 		})
@@ -101,21 +117,21 @@ var _ = Describe("qtls.Config generation", func() {
 					return nil, nil
 				},
 			}
-			qtlsConf := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{})
+			qtlsConf := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{}, nil, false)
 			Expect(qtlsConf.GetConfigForClient(nil)).To(BeNil())
 		})
 	})
 
 	Context("ClientSessionCache", func() {
 		It("doesn't set if absent", func() {
-			qtlsConf := tlsConfigToQtlsConfig(&tls.Config{}, nil, &mockExtensionHandler{})
+			qtlsConf := tlsConfigToQtlsConfig(&tls.Config{}, nil, &mockExtensionHandler{}, nil, false)
 			Expect(qtlsConf.ClientSessionCache).To(BeNil())
 		})
 
 		It("sets it, and puts and gets session states", func() {
 			csc := NewMockClientSessionCache(mockCtrl)
 			tlsConf := &tls.Config{ClientSessionCache: csc}
-			qtlsConf := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{})
+			qtlsConf := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{}, nil, false)
 			Expect(qtlsConf.ClientSessionCache).ToNot(BeNil())
 			// put something
 			csc.EXPECT().Put("foobar", gomock.Any())
@@ -129,7 +145,7 @@ var _ = Describe("qtls.Config generation", func() {
 		It("puts a nil session state", func() {
 			csc := NewMockClientSessionCache(mockCtrl)
 			tlsConf := &tls.Config{ClientSessionCache: csc}
-			qtlsConf := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{})
+			qtlsConf := tlsConfigToQtlsConfig(tlsConf, nil, &mockExtensionHandler{}, nil, false)
 			// put something
 			csc.EXPECT().Put("foobar", nil)
 			qtlsConf.ClientSessionCache.Put("foobar", nil)
diff --git a/session.go b/session.go
index 6756eb73..fd3cf3d5 100644
--- a/session.go
+++ b/session.go
@@ -274,6 +274,7 @@ var newSession = func(
 			},
 		},
 		tlsConf,
+		true, // TODO: make 0-RTT support configurable
 		s.rttStats,
 		logger,
 	)
@@ -370,6 +371,7 @@ var newClientSession = func(
 			onHandshakeComplete: func() { close(s.handshakeCompleteChan) },
 		},
 		tlsConf,
+		true, // TODO: make 0-RTT support configurable
 		s.rttStats,
 		logger,
 	)