diff --git a/src/structs.h b/src/structs.h
index 712382a..c47e291 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1777,7 +1777,7 @@
     char_u	*sv_name;	// points into "sn_all_vars" di_key
     typval_T	*sv_tv;		// points into "sn_vars" or "sn_all_vars" di_tv
     type_T	*sv_type;
-    int		sv_const;
+    int		sv_const;	// 0, ASSIGN_CONST or ASSIGN_FINAL
     int		sv_export;	// "export let var = val"
 };