diff --git a/src/backend.c b/src/backend.c
index aa51a92d..e829912e 100644
--- a/src/backend.c
+++ b/src/backend.c
@@ -257,11 +257,14 @@ static int sanity_check_all_drivers(const struct sr_context *ctx)
 			sr_err("No dev_list in driver %d ('%s').", i, d);
 			errors++;
 		}
+		/* Note: dev_clear() is optional. */
 		/* Note: config_get() is optional. */
 		if (!drivers[i]->config_set) {
 			sr_err("No config_set in driver %d ('%s').", i, d);
 			errors++;
 		}
+		/* Note: config_channel_set() is optional. */
+		/* Note: config_commit() is optional. */
 		if (!drivers[i]->config_list) {
 			sr_err("No config_list in driver %d ('%s').", i, d);
 			errors++;