diff --git a/include/hardware/sensors.h b/include/hardware/sensors.h
index 8c5fa16..92a8fd9 100644
--- a/include/hardware/sensors.h
+++ b/include/hardware/sensors.h
@@ -701,7 +701,7 @@
             int sensor_handle, int channel_handle, const struct sensors_direct_cfg_t *config);
 
     /*
-     * Reserved for future use.
+     * Reserved for future use, must be zero.
      */
     void (*reserved_procs[5])(void);