diff --git a/lib/resolv.rb b/lib/resolv.rb
index ff86e43..08a3624 100644
--- a/lib/resolv.rb
+++ b/lib/resolv.rb
@@ -37,6 +37,8 @@
 
 class Resolv
 
+  VERSION = "0.2.2"
+
   ##
   # Looks up the first IP address for +name+.
 
diff --git a/resolv.gemspec b/resolv.gemspec
index db256dc..6b83e30 100644
--- a/resolv.gemspec
+++ b/resolv.gemspec
@@ -1,6 +1,13 @@
+name = File.basename(__FILE__, ".gemspec")
+version = ["lib", Array.new(name.count("-")+1).join("/")].find do |dir|
+  break File.foreach(File.join(__dir__, dir, "#{name.tr('-', '/')}.rb")) do |line|
+    /^\s*VERSION\s*=\s*"(.*)"/ =~ line and break $1
+  end rescue nil
+end
+
 Gem::Specification.new do |spec|
-  spec.name          = "resolv"
-  spec.version       = "0.2.2"
+  spec.name          = name
+  spec.version       = version
   spec.authors       = ["Tanaka Akira"]
   spec.email         = ["akr@fsij.org"]