Update runtime files.
diff --git a/runtime/syntax/rrst.vim b/runtime/syntax/rrst.vim
index b643af3..3a56342 100644
--- a/runtime/syntax/rrst.vim
+++ b/runtime/syntax/rrst.vim
@@ -2,7 +2,7 @@
 " Language: reST with R code chunks
 " Maintainer: Alex Zvoleff, azvoleff@mail.sdsu.edu
 " Homepage: https://github.com/jalvesaq/R-Vim-runtime
-" Last Change: Tue Jun 28, 2016  08:53AM
+" Last Change: Thu Apr 05, 2018  11:06PM
 "
 " CONFIGURATION:
 "   To highlight chunk headers as R code, put in your vimrc:
@@ -14,7 +14,7 @@
 
 " load all of the rst info
 runtime syntax/rst.vim
-unlet b:current_syntax
+unlet! b:current_syntax
 
 " load all of the r syntax highlighting rules into @R
 syntax include @R syntax/r.vim