diff --git a/crypto/ecrdsa.c b/crypto/ecrdsa.c
index f981b31f4249..b3dd8a3ddeb7 100644
--- a/crypto/ecrdsa.c
+++ b/crypto/ecrdsa.c
@@ -252,6 +252,13 @@ static unsigned int ecrdsa_key_size(struct crypto_sig *tfm)
 	return ctx->pub_key.ndigits * sizeof(u64);
 }
 
+static unsigned int ecrdsa_max_size(struct crypto_sig *tfm)
+{
+	struct ecrdsa_ctx *ctx = crypto_sig_ctx(tfm);
+
+	return 2 * ctx->pub_key.ndigits * sizeof(u64);
+}
+
 static void ecrdsa_exit_tfm(struct crypto_sig *tfm)
 {
 }
@@ -260,6 +267,7 @@ static struct sig_alg ecrdsa_alg = {
 	.verify		= ecrdsa_verify,
 	.set_pub_key	= ecrdsa_set_pub_key,
 	.key_size	= ecrdsa_key_size,
+	.max_size	= ecrdsa_max_size,
 	.exit		= ecrdsa_exit_tfm,
 	.base = {
 		.cra_name	 = "ecrdsa",