diff --git a/README.md b/README.md
index dc4d2f7..c87e7fa 100644
--- a/README.md
+++ b/README.md
@@ -35,12 +35,12 @@ call plug#end()
 ## Configuration
 ### Select processor
 By default, the syntax highlighting only highlights the original 6502 instructions.
-To enable the undocumented instructions, the 65C02 instructions or the 65816 instructions, write this into `~/.vim/ftplugin/ca65.vim`:
+To enable the illegal/undocumented instructions, the 65C02 instructions or the 65816 instructions, write this into `~/.vim/ftplugin/ca65.vim`:
 ```vim
 " in ~/.vim/ftplugin/ca65.vim (or vimrc) 
-let g:ca65_undoc = 1  " enable the undocumented opcodes
-let g:ca65_65C02 = 1  " enable 65C02 instructions
-let g:ca65_65816 = 1  " enable 65816 instructions
+let g:ca65_illegal = 1  " enable the illegal 6502 opcodes
+let g:ca65_65C02 = 1    " enable 65C02 instructions
+let g:ca65_65816 = 1    " enable 65816 instructions
 ```
 
 ### Select filetype