diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index f50cf9f..f3de299 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -1306,4 +1306,12 @@
 void mbedtls_ssl_flight_free( mbedtls_ssl_flight_item *flight );
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
+#if defined(MBEDTLS_TEST_HOOKS)
+int ssl_check_dtls_clihlo_cookie(
+                          mbedtls_ssl_context *ssl,
+                          const unsigned char *cli_id, size_t cli_id_len,
+                          const unsigned char *in, size_t in_len,
+                          unsigned char *obuf, size_t buf_len, size_t *olen );
+#endif
+
 #endif /* ssl_internal.h */