diff --git a/routing/city_roads_loader.hpp b/routing/city_roads_loader.hpp
index 98b07f09a0..b3907d34f5 100644
--- a/routing/city_roads_loader.hpp
+++ b/routing/city_roads_loader.hpp
@@ -34,6 +34,7 @@ struct CityRoadsHeader
   }
 
   uint16_t m_version = 0;
+  // Field |m_endianness| is reserved for endianness of the section.
   uint16_t m_endianness = 0;
   uint32_t m_dataSize = 0;
 };