diff --git a/lib/pp.gemspec b/lib/pp.gemspec
index d4b0be83df..3f08f400c4 100644
--- a/lib/pp.gemspec
+++ b/lib/pp.gemspec
@@ -1,6 +1,6 @@
 Gem::Specification.new do |spec|
   spec.name          = "pp"
-  spec.version       = "0.3.0"
+  spec.version       = "0.4.0"
   spec.authors       = ["Tanaka Akira"]
   spec.email         = ["akr@fsij.org"]