diff --git a/ChangeLog b/ChangeLog
index 50c7e63b47de6c..12a00a1d8ac4f9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Jul 30 23:19:09 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* defs/default_gems: separate from tool/rbinstall.rb.
+
 Sat Jul 30 23:14:44 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* io.c (rb_io_each_byte): rbuf can be refreshed during yield.
diff --git a/defs/default_gems b/defs/default_gems
new file mode 100644
index 00000000000000..030d84f6f50094
--- /dev/null
+++ b/defs/default_gems
@@ -0,0 +1,7 @@
+# gem		versioning file			[executable files under bin]
+rake		lib/rake/version.rb		[rake]
+rdoc		lib/rdoc.rb			[rdoc ri]
+minitest	lib/minitest/unit.rb
+json		ext/json/lib/json/version.rb
+io-console	ext/io/console/io-console.gemspec
+bigdecimal	ext/bigdecimal/bigdecimal.gemspec
diff --git a/tool/rbinstall.rb b/tool/rbinstall.rb
index d081e1c3e03136..cec8c9f132cc43 100755
--- a/tool/rbinstall.rb
+++ b/tool/rbinstall.rb
@@ -539,16 +539,16 @@ class << (w = [])
   prepare "default gems", gem_dir, directories
 
   spec_dir = File.join(gem_dir, directories.grep(/^spec/)[0])
-  default_gems = [
-    ['rake', 'lib/rake/version.rb', ['rake']],
-    ['rdoc', 'lib/rdoc.rb', ['rdoc', 'ri']],
-    ['minitest', 'lib/minitest/unit.rb'],
-    ['json', 'ext/json/lib/json/version.rb'],
-    ['io-console', 'ext/io/console/io-console.gemspec'],
-    ['bigdecimal', 'ext/bigdecimal/bigdecimal.gemspec'],
-  ]
-
-  default_gems.each do |name, src, execs|
+  File.foreach(File.join(srcdir, "defs/default_gems")) do |line|
+    line.chomp!
+    line.sub!(/\s*#.*/, '')
+    next if line.empty?
+    words = []
+    line.scan(/\G\s*([^\[\]\s]+|\[([^\[\]]*)\])/) do
+      words << ($2 ? $2.split : $1)
+    end
+    name, src, execs = *words
+    next unless name and src
     execs ||= []
     src = File.join(srcdir, src)
     version = open(src) {|f| f.find {|s| /^\s*\w*VERSION\s*=(?!=)/ =~ s}} or next