Update runtime files.
diff --git a/runtime/ftplugin/scheme.vim b/runtime/ftplugin/scheme.vim
index 62fd327..5778594 100644
--- a/runtime/ftplugin/scheme.vim
+++ b/runtime/ftplugin/scheme.vim
@@ -1,6 +1,6 @@
 " Vim filetype plugin file
 " Language: Scheme (R7RS)
-" Last Change: 2018-03-05
+" Last Change: 2019 Nov 18
 " Author: Evan Hanson <evhan@foldling.org>
 " Maintainer: Evan Hanson <evhan@foldling.org>
 " Previous Maintainer: Sergey Khorev <sergey.khorev@gmail.com>
@@ -21,7 +21,7 @@
 
 let b:undo_ftplugin = 'setl lisp< comments< commentstring< define< iskeyword<'
 
-setl lispwords=case
+setl lispwords+=case
 setl lispwords+=define
 setl lispwords+=define-record-type
 setl lispwords+=define-syntax