diff --git a/.travis.yml b/.travis.yml
index ee0b1f0..931d9ad 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,9 +1,9 @@
 language: ruby
 
 rvm:
-  - 2.1
-  - 2.2
-  - 2.3
+  - 2.2.6
+  - 2.3.3
+  - 2.4.0
 
 install:
   - "gem install bundler"
diff --git a/Gemfile b/Gemfile
index 91282b7..46d32f1 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,10 +1,7 @@
 source 'https://rubygems.org'
 
-ruby_version = RUBY_VERSION
 paperclip_version = ENV['PAPERCLIP_VERSION']
 
 gem "paperclip", "~> #{paperclip_version}" if paperclip_version
 
-gem "activesupport", "< 5.0.0" if ruby_version =~ /^2\.1\./
-
 gemspec
diff --git a/paperclip-deflater.gemspec b/paperclip-deflater.gemspec
index ac49dee..3a8c4bf 100644
--- a/paperclip-deflater.gemspec
+++ b/paperclip-deflater.gemspec
@@ -10,16 +10,18 @@ Gem::Specification.new do |gem|
   gem.summary     = "Deflate Processor for Paperclip"
   gem.description = "Deflate Processor for Paperclip"
   gem.license     = "MIT"
-  gem.required_ruby_version = '~> 2.1'
 
   gem.files       = `git ls-files`.split("\n")
   gem.test_files  = `git ls-files -- {test,spec,features}/*`.split("\n")
   gem.executables = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
-  gem.require_paths = ['lib']
+  gem.require_paths = ["lib"]
 
-  gem.add_dependency "paperclip", ">= 3.4"
+  gem.required_ruby_version = [">= 2.1", "< 2.5"]
 
-  gem.add_development_dependency "rake"
-  gem.add_development_dependency "rspec", ">= 3.0"
-  gem.add_development_dependency "coveralls"
+  gem.add_runtime_dependency "paperclip", ">= 3.4", "< 6.0"
+
+  gem.add_development_dependency "rake", ">= 10.0", "< 13"
+  gem.add_development_dependency "rspec", ">= 3.0", "< 4"
+  gem.add_development_dependency "simplecov", "~> 0.12"
+  gem.add_development_dependency "coveralls", "~> 0.8"
 end