diff --git a/crypto/secp256k1/ext.h b/crypto/secp256k1/ext.h
index 9b043c724e..4accbbd8f6 100644
--- a/crypto/secp256k1/ext.h
+++ b/crypto/secp256k1/ext.h
@@ -128,7 +128,7 @@ int secp256k1_ext_scalar_mul(const secp256k1_context* ctx, unsigned char *point,
 	if (overflow || secp256k1_scalar_is_zero(&s)) {
 		ret = 0;
 	} else {
-		secp256k1_ecmult_const(&res, &ge, &s);
+		secp256k1_ecmult_const(&res, &ge, &s, 256);
 		secp256k1_ge_set_gej(&ge, &res);
 		/* Note: can't use secp256k1_pubkey_save here because it is not constant time. */
 		secp256k1_fe_normalize(&ge.x);