diff --git a/common.go b/common.go
index f57d932..a461ad9 100644
--- a/common.go
+++ b/common.go
@@ -5,8 +5,8 @@
 package tls
 
 import (
+	"crypto"
 	"crypto/rand"
-	"crypto/rsa"
 	"crypto/x509"
 	"io"
 	"strings"
@@ -255,7 +255,7 @@ func (c *Config) BuildNameToCertificate() {
 // A Certificate is a chain of one or more certificates, leaf first.
 type Certificate struct {
 	Certificate [][]byte
-	PrivateKey  *rsa.PrivateKey
+	PrivateKey  crypto.PrivateKey // supported types: *rsa.PrivateKey
 	// OCSPStaple contains an optional OCSP response which will be served
 	// to clients that request it.
 	OCSPStaple []byte
diff --git a/handshake_client.go b/handshake_client.go
index e39e59c..7364800 100644
--- a/handshake_client.go
+++ b/handshake_client.go
@@ -234,7 +234,7 @@ func (c *Conn) clientHandshake() error {
 		digest := make([]byte, 0, 36)
 		digest = finishedHash.serverMD5.Sum(digest)
 		digest = finishedHash.serverSHA1.Sum(digest)
-		signed, err := rsa.SignPKCS1v15(c.config.rand(), c.config.Certificates[0].PrivateKey, crypto.MD5SHA1, digest)
+		signed, err := rsa.SignPKCS1v15(c.config.rand(), c.config.Certificates[0].PrivateKey.(*rsa.PrivateKey), crypto.MD5SHA1, digest)
 		if err != nil {
 			return c.sendAlert(alertInternalError)
 		}
diff --git a/key_agreement.go b/key_agreement.go
index b531717..c3c1664 100644
--- a/key_agreement.go
+++ b/key_agreement.go
@@ -44,7 +44,7 @@ func (ka rsaKeyAgreement) processClientKeyExchange(config *Config, ckx *clientKe
 		ciphertext = ckx.ciphertext[2:]
 	}
 
-	err = rsa.DecryptPKCS1v15SessionKey(config.rand(), config.Certificates[0].PrivateKey, ciphertext, preMasterSecret)
+	err = rsa.DecryptPKCS1v15SessionKey(config.rand(), config.Certificates[0].PrivateKey.(*rsa.PrivateKey), ciphertext, preMasterSecret)
 	if err != nil {
 		return nil, err
 	}
@@ -147,7 +147,7 @@ Curve:
 	copy(serverECDHParams[4:], ecdhePublic)
 
 	md5sha1 := md5SHA1Hash(clientHello.random, hello.random, serverECDHParams)
-	sig, err := rsa.SignPKCS1v15(config.rand(), config.Certificates[0].PrivateKey, crypto.MD5SHA1, md5sha1)
+	sig, err := rsa.SignPKCS1v15(config.rand(), config.Certificates[0].PrivateKey.(*rsa.PrivateKey), crypto.MD5SHA1, md5sha1)
 	if err != nil {
 		return nil, errors.New("failed to sign ECDHE parameters: " + err.Error())
 	}