diff --git a/src/vim.h b/src/vim.h
index f3e87fe..8636c56 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2474,10 +2474,12 @@
 #define TFN_QUIET	2	/* no error messages */
 #define TFN_NO_AUTOLOAD	4	/* do not use script autoloading */
 #define TFN_NO_DEREF	8	/* do not dereference a Funcref */
+#define TFN_READ_ONLY	16	/* will not change the var */
 
 /* Values for get_lval() flags argument: */
 #define GLV_QUIET	TFN_QUIET	/* no error messages */
 #define GLV_NO_AUTOLOAD	TFN_NO_AUTOLOAD	/* do not use script autoloading */
+#define GLV_READ_ONLY	TFN_READ_ONLY	/* will not change the var */
 
 #define DO_NOT_FREE_CNT 99999	/* refcount for dict or list that should not
 				   be freed. */