diff --git a/ChangeLog b/ChangeLog
index dbcfc4f1ef..eced2dc54e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Dec 27 07:32:07 2010  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
+
+	* lib/optparse.rb (OptionParser#compsys): escape brackets too.
+	  [ruby-dev:42754]
+
 Mon Dec 27 01:30:08 2010  Tanaka Akira  <akr@fsij.org>
 
 	* ext/socket/mkconstants.rb: add IF_NAMESIZE.
diff --git a/lib/optparse.rb b/lib/optparse.rb
index c91334d92e..70fda81207 100644
--- a/lib/optparse.rb
+++ b/lib/optparse.rb
@@ -763,7 +763,7 @@ XXX
     to << "#compdef #{name}\n"
     to << COMPSYS_HEADER
     visit(:compsys, {}, {}) {|o, d|
-      to << %Q[  "#{o}[#{d.gsub(/\"/, '\"')}]" \\\n]
+      to << %Q[  "#{o}[#{d.gsub(/[\"\[\]]/, '\\\\\&')}]" \\\n]
     }
     to << "  '*:file:_files' && return 0\n"
   end