diff --git a/runtime/ftplugin/man.vim b/runtime/ftplugin/man.vim
index 3fb22a1..242a771 100644
--- a/runtime/ftplugin/man.vim
+++ b/runtime/ftplugin/man.vim
@@ -1,7 +1,7 @@
 " Vim filetype plugin file
 " Language:	man
 " Maintainer:	SungHyun Nam <goweol@gmail.com>
-" Last Change:	2010 Nov 29
+" Last Change:	2011 Jul 25
 
 " To make the ":Man" command available before editing a manual page, source
 " this script from your startup vimrc file.
@@ -17,7 +17,9 @@
 
   " Ensure Vim is not recursively invoked (man-db does this)
   " when doing ctrl-[ on a man page reference.
-  let $MANPAGER = ""
+  if exists("$MANPAGER")
+    let $MANPAGER = ""
+  endif
 
   " allow dot and dash in manual page name.
   setlocal iskeyword+=\.,-