diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 4cdd87e..ccf382e 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -107,6 +107,7 @@
 #define MBEDTLS_SSL_EXT_ID_ENCRYPT_THEN_MAC           25
 #define MBEDTLS_SSL_EXT_ID_EXTENDED_MASTER_SECRET     26
 #define MBEDTLS_SSL_EXT_ID_SESSION_TICKET             27
+#define MBEDTLS_SSL_EXT_ID_RECORD_SIZE_LIMIT          28
 
 /* Utility for translating IANA extension type. */
 uint32_t mbedtls_ssl_get_extension_id(unsigned int extension_type);
@@ -167,6 +168,7 @@
      MBEDTLS_SSL_EXT_MASK(CERT_AUTH)                              | \
      MBEDTLS_SSL_EXT_MASK(POST_HANDSHAKE_AUTH)                    | \
      MBEDTLS_SSL_EXT_MASK(SIG_ALG_CERT)                           | \
+     MBEDTLS_SSL_EXT_MASK(RECORD_SIZE_LIMIT)                      | \
      MBEDTLS_SSL_TLS1_3_EXT_MASK_UNRECOGNIZED)
 
 /* RFC 8446 section 4.2. Allowed extensions for EncryptedExtensions */
@@ -179,7 +181,8 @@
      MBEDTLS_SSL_EXT_MASK(ALPN)                                   | \
      MBEDTLS_SSL_EXT_MASK(CLI_CERT_TYPE)                          | \
      MBEDTLS_SSL_EXT_MASK(SERV_CERT_TYPE)                         | \
-     MBEDTLS_SSL_EXT_MASK(EARLY_DATA))
+     MBEDTLS_SSL_EXT_MASK(EARLY_DATA)                             | \
+     MBEDTLS_SSL_EXT_MASK(RECORD_SIZE_LIMIT))
 
 /* RFC 8446 section 4.2. Allowed extensions for CertificateRequest */
 #define MBEDTLS_SSL_TLS1_3_ALLOWED_EXTS_OF_CR                                  \
@@ -2662,6 +2665,13 @@
                                       const unsigned char *end);
 #endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */
 
+#if defined(MBEDTLS_SSL_RECORD_SIZE_LIMIT)
+MBEDTLS_CHECK_RETURN_CRITICAL
+int mbedtls_ssl_tls13_parse_record_size_limit_ext(mbedtls_ssl_context *ssl,
+                                                  const unsigned char *buf,
+                                                  const unsigned char *end);
+#endif /* MBEDTLS_SSL_RECORD_SIZE_LIMIT */
+
 #if defined(MBEDTLS_SSL_ALPN)
 MBEDTLS_CHECK_RETURN_CRITICAL
 int mbedtls_ssl_parse_alpn_ext(mbedtls_ssl_context *ssl,