diff --git a/src/config.h b/src/config.h
index 0c7ea5f..f5a8a77 100644
--- a/src/config.h
+++ b/src/config.h
@@ -21,6 +21,7 @@
 class StorageInterface;
 
 enum class RootClientTokenOwner {
+  // Keep order as it's used with order comparison operators.
   kNone,
   kClient,
   kCloud,