diff --git a/photon/libc/sys/horizon/sys/_fconst.h b/photon/libc/sys/horizon/sys/_fconst.h
index 202a7db..afb7584 100644
--- a/photon/libc/sys/horizon/sys/_fconst.h
+++ b/photon/libc/sys/horizon/sys/_fconst.h
@@ -1,8 +1,10 @@
 #ifndef SYS_HORIZON_SYS__FCONST_H_
 #define SYS_HORIZON_SYS__FCONST_H_
 
+/* Must use the value of horizon.io.NAME_MAX */
 #define __FILENAME_MAX 255
 
+/* Must use the values from horizon.io.Whence */
 #define __SEEK_SET 0
 #define __SEEK_CUR 1
 #define __SEEK_END 2