diff --git a/is-my-code-constant-time?.md b/is-my-code-constant-time?.md
index c6c6ead..d44c21e 100644
--- a/is-my-code-constant-time?.md
+++ b/is-my-code-constant-time?.md
@@ -66,7 +66,7 @@ type Curve interface {
 	ECDH(local *PrivateKey, remote *PublicKey) ([]byte, error)
         
         // SM2ECDH performs a SM2 exchange and returns the shared secret.
-        SM2ECDH(local *PrivateKey, remote *PublicKey, localUID, remoteUID []byte, keyLen int) ([]byte, error)
+        SM2ECDH(enc, local *PrivateKey, remote *PublicKey, localUID, remoteUID []byte, keyLen int) ([]byte, error)
 
 	// GenerateKey generates a new PrivateKey from rand.
 	GenerateKey(rand io.Reader) (*PrivateKey, error)