diff --git a/common.go b/common.go
index 22d75f2..e261573 100644
--- a/common.go
+++ b/common.go
@@ -30,6 +30,7 @@ const (
 	VersionTLS13Draft18 = 0x7f00 | 18
 	VersionTLS13Draft21 = 0x7f00 | 21
 	VersionTLS13Draft22 = 0x7f00 | 22
+	VersionTLS13Draft23 = 0x7f00 | 23
 )
 
 const (
@@ -40,7 +41,7 @@ const (
 	maxWarnAlertCount = 5            // maximum number of consecutive warning alerts
 
 	minVersion = VersionTLS12
-	maxVersion = VersionTLS13Draft22
+	maxVersion = VersionTLS13Draft23
 )
 
 // TLS record types.
@@ -87,12 +88,12 @@ const (
 	extensionALPN                uint16 = 16
 	extensionSCT                 uint16 = 18 // https://tools.ietf.org/html/rfc6962#section-6
 	extensionSessionTicket       uint16 = 35
-	extensionKeyShare            uint16 = 40
 	extensionPreSharedKey        uint16 = 41
 	extensionEarlyData           uint16 = 42
 	extensionSupportedVersions   uint16 = 43
 	extensionPSKKeyExchangeModes uint16 = 45
 	extensionCAs                 uint16 = 47
+	extensionKeyShare            uint16 = 51
 	extensionNextProtoNeg        uint16 = 13172 // not IANA assigned
 	extensionRenegotiationInfo   uint16 = 0xff01
 )
@@ -858,7 +859,7 @@ var configSuppVersArray = [...]uint16{VersionTLS13, VersionTLS12, VersionTLS11,
 // with TLS 1.3 draft versions included.
 //
 // TODO: remove once TLS 1.3 is finalised.
-var tls13DraftSuppVersArray = [...]uint16{VersionTLS13Draft22, VersionTLS12, VersionTLS11, VersionTLS10, VersionSSL30}
+var tls13DraftSuppVersArray = [...]uint16{VersionTLS13Draft23, VersionTLS12, VersionTLS11, VersionTLS10, VersionSSL30}
 
 // getSupportedVersions returns the protocol versions that are supported by the
 // current configuration.