diff --git a/tests/include/test/ssl_helpers.h b/tests/include/test/ssl_helpers.h
index d03c624..b45e969 100644
--- a/tests/include/test/ssl_helpers.h
+++ b/tests/include/test/ssl_helpers.h
@@ -193,6 +193,10 @@
 
 #endif /* MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED */
 
+#if defined(MBEDTLS_SSL_HANDSHAKE_WITH_CERT_ENABLED)
+int rng_get(void *p_rng, unsigned char *output, size_t output_len);
+#endif
+
 /*
  * This function can be passed to mbedtls to receive output logs from it. In
  * this case, it will count the instances of a mbedtls_test_ssl_log_pattern