diff --git a/library/ssl_tls12_client.c b/library/ssl_tls12_client.c
index a56e8cd11c..17ea5e92d0 100644
--- a/library/ssl_tls12_client.c
+++ b/library/ssl_tls12_client.c
@@ -2283,6 +2283,8 @@ start_processing:
          * However since we only support secp256r1 for now, we check only
          * that TLS ID here
          */
+        MBEDTLS_SSL_CHK_BUF_READ_PTR(p, end, 3);
+
         uint16_t read_tls_id = MBEDTLS_GET_UINT16_BE(p, 1);
         uint16_t exp_tls_id = mbedtls_ssl_get_tls_id_from_ecp_group_id(
             MBEDTLS_ECP_DP_SECP256R1);