diff --git a/README.md b/README.md
index c0f0d18..e02bcef 100644
--- a/README.md
+++ b/README.md
@@ -23,7 +23,7 @@ gem 'middleman-imageoptim', '~> 0.2.1'
 ### Middleman ≥ 4.0
 
 ```ruby
-gem "middleman-imageoptim", '~> 0.3.0'
+gem "middleman-imageoptim", '~> 0.4.0'
 ```
 
 ## Usage
@@ -70,6 +70,10 @@ end
 
 ## Changelog
 
+##### `0.4.0`
+- Use latest `:image_optim` and `:image_optim_pack` gems.
+- Remove deprecated `:image_optim` extension name.
+
 ##### `0.3.0`
 - https://github.com/plasticine/middleman-imageoptim/compare/v0.2.1...a539cae
 
diff --git a/lib/middleman-imageoptim.rb b/lib/middleman-imageoptim.rb
index dc7973e..b07e672 100644
--- a/lib/middleman-imageoptim.rb
+++ b/lib/middleman-imageoptim.rb
@@ -10,10 +10,3 @@
   require 'middleman-imageoptim/extension'
   ::Middleman::Imageoptim::Extension
 end
-
-::Middleman::Extensions.register(:image_optim) do
-  warn ':image_optim is deprecated. Please use `:imageoptim` instead.'
-
-  require 'middleman-imageoptim/extension'
-  ::Middleman::Imageoptim::Extension
-end
diff --git a/lib/middleman-imageoptim/version.rb b/lib/middleman-imageoptim/version.rb
index b441134..a7135ec 100644
--- a/lib/middleman-imageoptim/version.rb
+++ b/lib/middleman-imageoptim/version.rb
@@ -1,6 +1,6 @@
 module Middleman
   module Imageoptim
     PACKAGE = 'middleman-imageoptim'.freeze
-    VERSION = '0.3.0'.freeze
+    VERSION = '0.4.0'.freeze
   end
 end
diff --git a/middleman-imageoptim.gemspec b/middleman-imageoptim.gemspec
index f261e14..a2b06d5 100644
--- a/middleman-imageoptim.gemspec
+++ b/middleman-imageoptim.gemspec
@@ -18,8 +18,8 @@ Gem::Specification.new do |gem|
 
   gem.add_dependency 'middleman-core', ['>= 3.1']
   gem.add_dependency 'middleman-cli'
-  gem.add_dependency 'image_optim', '~> 0.25.0'
-  gem.add_dependency 'image_optim_pack', '~> 0.2.1'
+  gem.add_dependency 'image_optim', '~> 0.26'
+  gem.add_dependency 'image_optim_pack', '~> 0.6'
 
   gem.add_development_dependency 'appraisal'
   gem.add_development_dependency 'aruba'