diff --git a/openpgp/clearsign/clearsign.go b/openpgp/clearsign/clearsign.go
index 460347af..245a66f1 100644
--- a/openpgp/clearsign/clearsign.go
+++ b/openpgp/clearsign/clearsign.go
@@ -337,6 +337,7 @@ func (d *dashEscaper) Close() (err error) {
 		sig.Hash = d.hashTypes[i]
 		sig.CreationTime = t
 		sig.IssuerKeyId = &k.KeyId
+		sig.IssuerKeyVersion = uint8(k.Version)
 		sig.IssuerFingerprint = k.Fingerprint
 		sig.Notations = d.config.Notations()
 		sigLifetimeSecs := d.config.SigLifetime()
diff --git a/openpgp/packet/signature.go b/openpgp/packet/signature.go
index 4490fdf8..8dd6213b 100644
--- a/openpgp/packet/signature.go
+++ b/openpgp/packet/signature.go
@@ -87,11 +87,13 @@ type Signature struct {
 
 	// The following are optional so are nil when not included in the
 	// signature.
+	// The exception is IssuerKeyVersion, which defaults to 0.
 
 	SigLifetimeSecs, KeyLifetimeSecs                        *uint32
 	PreferredSymmetric, PreferredHash, PreferredCompression []uint8
 	PreferredCipherSuites                                   [][2]uint8
 	IssuerKeyId                                             *uint64
+	IssuerKeyVersion                                        uint8
 	IssuerFingerprint                                       []byte
 	SignerUserId                                            *string
 	IsPrimaryId                                             *bool
@@ -637,6 +639,7 @@ func parseSignatureSubpacket(sig *Signature, subpacket []byte, isHashed bool) (r
 		if v >= 5 && l != 32 || v < 5 && l != 20 {
 			return nil, errors.StructuralError("bad fingerprint length")
 		}
+		sig.IssuerKeyVersion = subpacket[0]
 		sig.IssuerFingerprint = make([]byte, l)
 		copy(sig.IssuerFingerprint, subpacket[1:])
 		sig.IssuerKeyId = new(uint64)
@@ -694,14 +697,14 @@ func subpacketLengthLength(length int) int {
 }
 
 func (sig *Signature) CheckKeyIdOrFingerprint(pk *PublicKey) bool {
-	if sig.IssuerFingerprint != nil && len(sig.IssuerFingerprint) >= 20 {
-		return bytes.Equal(sig.IssuerFingerprint, pk.Fingerprint)
+	if sig.IssuerKeyVersion != 0 && len(sig.IssuerFingerprint) >= 20 {
+		return int(sig.IssuerKeyVersion) == pk.Version && bytes.Equal(sig.IssuerFingerprint, pk.Fingerprint)
 	}
 	return sig.IssuerKeyId != nil && *sig.IssuerKeyId == pk.KeyId
 }
 
 func (sig *Signature) CheckKeyIdOrFingerprintExplicit(fingerprint []byte, keyId uint64) bool {
-	if sig.IssuerFingerprint != nil && len(sig.IssuerFingerprint) >= 20 && fingerprint != nil {
+	if sig.IssuerKeyVersion != 0 && len(sig.IssuerFingerprint) >= 20 && fingerprint != nil {
 		return bytes.Equal(sig.IssuerFingerprint, fingerprint)
 	}
 	return sig.IssuerKeyId != nil && *sig.IssuerKeyId == keyId
@@ -918,6 +921,7 @@ func (sig *Signature) Sign(h hash.Hash, priv *PrivateKey, config *Config) (err e
 		return errors.ErrDummyPrivateKey("dummy key found")
 	}
 	sig.Version = priv.PublicKey.Version
+	sig.IssuerKeyVersion = uint8(priv.PublicKey.Version)
 	sig.IssuerFingerprint = priv.PublicKey.Fingerprint
 	if sig.Version < 6 && config.RandomizeSignaturesViaNotation() {
 		sig.removeNotationsWithName(SaltNotationName)
@@ -933,7 +937,7 @@ func (sig *Signature) Sign(h hash.Hash, priv *PrivateKey, config *Config) (err e
 		}
 		sig.Notations = append(sig.Notations, &notation)
 	}
-	sig.outSubpackets, err = sig.buildSubpackets(priv.PublicKey, config)
+	sig.outSubpackets, err = sig.buildSubpackets(config)
 	if err != nil {
 		return err
 	}
@@ -1254,7 +1258,7 @@ type outputSubpacket struct {
 	contents      []byte
 }
 
-func (sig *Signature) buildSubpackets(issuer PublicKey, config *Config) (subpackets []outputSubpacket, err error) {
+func (sig *Signature) buildSubpackets(config *Config) (subpackets []outputSubpacket, err error) {
 	creationTime := make([]byte, 4)
 	binary.BigEndian.PutUint32(creationTime, uint32(sig.CreationTime.Unix()))
 	// Signature Creation Time
@@ -1391,8 +1395,8 @@ func (sig *Signature) buildSubpackets(issuer PublicKey, config *Config) (subpack
 		subpackets = append(subpackets, outputSubpacket{true, embeddedSignatureSubpacket, true, buf.Bytes()})
 	}
 	// Issuer Fingerprint
-	if sig.IssuerFingerprint != nil {
-		contents := append([]uint8{uint8(issuer.Version)}, sig.IssuerFingerprint...)
+	if sig.IssuerKeyVersion != 0 && sig.IssuerFingerprint != nil {
+		contents := append([]uint8{sig.IssuerKeyVersion}, sig.IssuerFingerprint...)
 		subpackets = append(subpackets, outputSubpacket{true, issuerFingerprintSubpacket, sig.Version >= 5, contents})
 	}
 	// Intended Recipient Fingerprint
diff --git a/openpgp/v2/read.go b/openpgp/v2/read.go
index 7980c9b2..b04c67e4 100644
--- a/openpgp/v2/read.go
+++ b/openpgp/v2/read.go
@@ -297,8 +297,8 @@ func newSignatureCandidate(ops *packet.OnePassSignature) (sigCandidate *Signatur
 		HashAlgorithm:     ops.Hash,
 		PubKeyAlgo:        ops.PubKeyAlgo,
 		IssuerKeyId:       ops.KeyId,
-		Salt:              ops.Salt,
 		IssuerFingerprint: ops.KeyFingerprint,
+		Salt:              ops.Salt,
 	}
 	sigCandidate.Hash, sigCandidate.WrappedHash, sigCandidate.SignatureError = hashForSignature(
 		sigCandidate.HashAlgorithm,
@@ -331,18 +331,20 @@ func newSignatureCandidateFromSignature(sig *packet.Signature) (sigCandidate *Si
 }
 
 func (sc *SignatureCandidate) validate() bool {
+	if sc.CorrespondingSig == nil {
+		return false
+	}
 	correspondingSig := sc.CorrespondingSig
 	invalidV3 := sc.OPSVersion == 3 && correspondingSig.Version == 6
-	invalidV6 := (sc.OPSVersion == 6 && correspondingSig.Version != 6) ||
-		(sc.OPSVersion == 6 && !bytes.Equal(sc.IssuerFingerprint, correspondingSig.IssuerFingerprint)) ||
-		(sc.OPSVersion == 6 && !bytes.Equal(sc.Salt, correspondingSig.Salt()))
-	return correspondingSig != nil &&
+	invalidV6 := sc.OPSVersion == 6 &&
+		(correspondingSig.Version != 6 ||
+			!bytes.Equal(sc.IssuerFingerprint, correspondingSig.IssuerFingerprint) ||
+			!bytes.Equal(sc.Salt, correspondingSig.Salt()))
+	return !invalidV3 && !invalidV6 &&
 		sc.SigType == correspondingSig.SigType &&
 		sc.HashAlgorithm == correspondingSig.Hash &&
 		sc.PubKeyAlgo == correspondingSig.PubKeyAlgo &&
-		sc.IssuerKeyId == *correspondingSig.IssuerKeyId &&
-		!invalidV3 &&
-		!invalidV6
+		sc.IssuerKeyId == *correspondingSig.IssuerKeyId
 }
 
 // readSignedMessage reads a possibly signed message if mdin is non-zero then
diff --git a/openpgp/v2/write.go b/openpgp/v2/write.go
index 0692cec6..804a895a 100644
--- a/openpgp/v2/write.go
+++ b/openpgp/v2/write.go
@@ -910,6 +910,7 @@ func createSignaturePacket(signer *packet.PublicKey, sigType packet.SignatureTyp
 		Hash:              hash,
 		CreationTime:      config.Now(),
 		IssuerKeyId:       &signer.KeyId,
+		IssuerKeyVersion:  uint8(signer.Version),
 		IssuerFingerprint: signer.Fingerprint,
 		Notations:         config.Notations(),
 		SigLifetimeSecs:   &sigLifetimeSecs,
diff --git a/openpgp/write.go b/openpgp/write.go
index 84bc27d8..f66f8ff5 100644
--- a/openpgp/write.go
+++ b/openpgp/write.go
@@ -566,6 +566,7 @@ func createSignaturePacket(signer *packet.PublicKey, sigType packet.SignatureTyp
 		Hash:              hash,
 		CreationTime:      config.Now(),
 		IssuerKeyId:       &signer.KeyId,
+		IssuerKeyVersion:  uint8(signer.Version),
 		IssuerFingerprint: signer.Fingerprint,
 		Notations:         config.Notations(),
 		SigLifetimeSecs:   &sigLifetimeSecs,