Update runtime files.
diff --git a/runtime/syntax/rnoweb.vim b/runtime/syntax/rnoweb.vim
index 665acc5..b2ba17d 100644
--- a/runtime/syntax/rnoweb.vim
+++ b/runtime/syntax/rnoweb.vim
@@ -1,7 +1,7 @@
" Vim syntax file
" Language: R noweb Files
" Maintainer: Johannes Ranke <jranke@uni-bremen.de>
-" Last Change: Sat Feb 06, 2016 06:47AM
+" Last Change: Thu Apr 05, 2018 11:06PM
" Version: 0.9.1
" Remarks: - This file is inspired by the proposal of
" Fernando Henrique Ferraz Pereira da Rosa <feferraz@ime.usp.br>
@@ -16,7 +16,7 @@
" Extension of Tex clusters {{{1
runtime syntax/tex.vim
-unlet b:current_syntax
+unlet! b:current_syntax
syn cluster texMatchGroup add=@rnoweb
syn cluster texMathMatchGroup add=rnowebSexpr