diff --git a/internal/handshake/updatable_aead.go b/internal/handshake/updatable_aead.go
index e086846c..a08824de 100644
--- a/internal/handshake/updatable_aead.go
+++ b/internal/handshake/updatable_aead.go
@@ -43,7 +43,7 @@ func setKeyUpdateInterval() {
 type updatableAEAD struct {
 	suite cipherSuite
 
-	keyPhase          protocol.KeyPhaseBit
+	keyPhase          protocol.KeyPhase
 	largestAcked      protocol.PacketNumber
 	keyUpdateInterval uint64
 
@@ -85,7 +85,7 @@ func newUpdatableAEAD(logger utils.Logger) *updatableAEAD {
 }
 
 func (a *updatableAEAD) rollKeys() {
-	a.keyPhase = a.keyPhase.Next()
+	a.keyPhase++
 	a.firstRcvdWithCurrentKey = protocol.InvalidPacketNumber
 	a.firstSentWithCurrentKey = protocol.InvalidPacketNumber
 	a.numRcvdWithCurrentKey = 0
@@ -136,7 +136,7 @@ func (a *updatableAEAD) SetWriteKey(suite cipherSuite, trafficSecret []byte) {
 
 func (a *updatableAEAD) Open(dst, src []byte, pn protocol.PacketNumber, kp protocol.KeyPhaseBit, ad []byte) ([]byte, error) {
 	binary.BigEndian.PutUint64(a.nonceBuf[len(a.nonceBuf)-8:], uint64(pn))
-	if kp != a.keyPhase {
+	if kp != a.keyPhase.Bit() {
 		if a.firstRcvdWithCurrentKey == protocol.InvalidPacketNumber || pn < a.firstRcvdWithCurrentKey {
 			if a.prevRcvAEAD == nil {
 				// This can only occur when the first packet received has key phase 1.
@@ -205,11 +205,11 @@ func (a *updatableAEAD) shouldInitiateKeyUpdate() bool {
 		return false
 	}
 	if a.numRcvdWithCurrentKey >= a.keyUpdateInterval {
-		a.logger.Debugf("Received %d packets with current key phase. Initiating key update to the next key phase: %s", a.numRcvdWithCurrentKey, a.keyPhase.Next())
+		a.logger.Debugf("Received %d packets with current key phase. Initiating key update to the next key phase: %s", a.numRcvdWithCurrentKey, a.keyPhase+1)
 		return true
 	}
 	if a.numSentWithCurrentKey >= a.keyUpdateInterval {
-		a.logger.Debugf("Sent %d packets with current key phase. Initiating key update to the next key phase: %s", a.numSentWithCurrentKey, a.keyPhase.Next())
+		a.logger.Debugf("Sent %d packets with current key phase. Initiating key update to the next key phase: %s", a.numSentWithCurrentKey, a.keyPhase+1)
 		return true
 	}
 	return false
@@ -219,7 +219,7 @@ func (a *updatableAEAD) KeyPhase() protocol.KeyPhaseBit {
 	if a.shouldInitiateKeyUpdate() {
 		a.rollKeys()
 	}
-	return a.keyPhase
+	return a.keyPhase.Bit()
 }
 
 func (a *updatableAEAD) Overhead() int {
diff --git a/internal/protocol/key_phase.go b/internal/protocol/key_phase.go
index 693aeb15..2ebc3f92 100644
--- a/internal/protocol/key_phase.go
+++ b/internal/protocol/key_phase.go
@@ -1,5 +1,12 @@
 package protocol
 
+// KeyPhase is the key phase
+type KeyPhase uint64
+
+func (p KeyPhase) Bit() KeyPhaseBit {
+	return p%2 == 1
+}
+
 // KeyPhaseBit is the key phase bit
 type KeyPhaseBit bool
 
@@ -16,7 +23,3 @@ func (p KeyPhaseBit) String() string {
 	}
 	return "1"
 }
-
-func (p KeyPhaseBit) Next() KeyPhaseBit {
-	return !p
-}
diff --git a/internal/protocol/key_phase_test.go b/internal/protocol/key_phase_test.go
index 67e3aabf..da06513e 100644
--- a/internal/protocol/key_phase_test.go
+++ b/internal/protocol/key_phase_test.go
@@ -11,8 +11,12 @@ var _ = Describe("Key Phases", func() {
 		Expect(KeyPhaseOne.String()).To(Equal("1"))
 	})
 
-	It("returns the next key phase", func() {
-		Expect(KeyPhaseZero.Next()).To(Equal(KeyPhaseOne))
-		Expect(KeyPhaseOne.Next()).To(Equal(KeyPhaseZero))
+	It("converts the key phase to the key phase bit", func() {
+		Expect(KeyPhase(0).Bit()).To(Equal(KeyPhaseZero))
+		Expect(KeyPhase(2).Bit()).To(Equal(KeyPhaseZero))
+		Expect(KeyPhase(4).Bit()).To(Equal(KeyPhaseZero))
+		Expect(KeyPhase(1).Bit()).To(Equal(KeyPhaseOne))
+		Expect(KeyPhase(3).Bit()).To(Equal(KeyPhaseOne))
+		Expect(KeyPhase(5).Bit()).To(Equal(KeyPhaseOne))
 	})
 })