diff --git a/openpgp/packet/private_key.go b/openpgp/packet/private_key.go
index 98cc14b..99b628f 100644
--- a/openpgp/packet/private_key.go
+++ b/openpgp/packet/private_key.go
@@ -196,8 +196,8 @@ func (pk *PrivateKey) Decrypt(passphrase []byte) error {
 	block := pk.cipher.new(key)
 	cfb := cipher.NewCFBDecrypter(block, pk.iv)
 
-	data := pk.encryptedData
-	cfb.XORKeyStream(data, data)
+	data := make([]byte, len(pk.encryptedData))
+	cfb.XORKeyStream(data, pk.encryptedData)
 
 	if pk.sha1Checksum {
 		if len(data) < sha1.Size {
diff --git a/openpgp/packet/private_key_test.go b/openpgp/packet/private_key_test.go
index 35d8951..6a6197a 100644
--- a/openpgp/packet/private_key_test.go
+++ b/openpgp/packet/private_key_test.go
@@ -38,6 +38,12 @@ func TestPrivateKeyRead(t *testing.T) {
 			continue
 		}
 
+		err = privKey.Decrypt([]byte("wrong password"))
+		if err == nil {
+			t.Errorf("#%d: decrypted with incorrect key", i)
+			continue
+		}
+
 		err = privKey.Decrypt([]byte("testing"))
 		if err != nil {
 			t.Errorf("#%d: failed to decrypt: %s", i, err)