diff --git a/src/vim.h b/src/vim.h
index 9da878e..c43ec83 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1992,7 +1992,8 @@
 #define VV_ECHOSPACE	93
 #define VV_ARGV		94
 #define VV_COLLATE      95
-#define VV_LEN		96	// number of v: vars
+#define VV_DISALLOW_LET 96	// TODO: remove again
+#define VV_LEN		97	// number of v: vars
 
 // used for v_number in VAR_BOOL and VAR_SPECIAL
 #define VVAL_FALSE	0L	// VAR_BOOL