diff --git a/.circleci/config.yml b/.circleci/config.yml
index 77dd162..2471382 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -7,7 +7,9 @@ jobs:
   build:
     docker:
       # specify the version you desire here
-       - image: circleci/ruby:2.4.1-node-browsers
+       - image: circleci/ruby:2.5-stretch
+         environment:
+          BUNDLER_VERSION: 2.0.1
 
     working_directory: ~/repo
 
@@ -20,11 +22,16 @@ jobs:
           - v1-dependencies-{{ checksum "Gemfile.lock" }}
           # fallback to using the latest cache if no exact match is found
           - v1-dependencies-
+      - run:
+          name: install dependencies
+          command: |
+            gem update --system
+            gem install bundler
 
       - run:
           name: install dependencies
           command: |
-            bundle install --jobs=4 --retry=3 --path vendor/bundle
+            bundle install
       - save_cache:
           paths:
             - ./vendor/bundle
diff --git a/.gitignore b/.gitignore
index b04a8c8..e0a7553 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,6 +6,7 @@
 /pkg/
 /spec/reports/
 /tmp/
+/vendor/
 
 # rspec failure tracking
 .rspec_status
diff --git a/Gemfile b/Gemfile
index eba2cf2..06be578 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,4 +1,4 @@
-source "https://rubygems.org"
+source 'https://rubygems.org'
 
 # Specify your gem's dependencies in simple-redis-lock.gemspec
 gemspec
diff --git a/Gemfile.lock b/Gemfile.lock
index 2985d1a..5a8df78 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -26,7 +26,6 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  bundler (~> 2.0)
   rake (~> 10.0)
   rspec (~> 3.0)
   simple-redis-lock!
diff --git a/simple-redis-lock.gemspec b/simple-redis-lock.gemspec
index 95f8a47..9b2a096 100644
--- a/simple-redis-lock.gemspec
+++ b/simple-redis-lock.gemspec
@@ -1,4 +1,3 @@
-
 lib = File.expand_path('../lib', __FILE__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require 'simple_redis_lock/version'
@@ -6,18 +5,18 @@ require 'simple_redis_lock/version'
 Gem::Specification.new do |spec|
   spec.name          = 'simple-redis-lock'
   spec.version       = SimpleRedisLock::VERSION
-  spec.authors          = ['Hint']
+  spec.authors       = ['Hint']
   spec.email         = ['maicol.bentancor@gmail.com']
 
-  spec.summary       = 'Simple redis lock'
-  spec.license       = 'MIT'
+  spec.summary               = 'Simple redis lock'
+  spec.license               = 'MIT'
+  spec.required_ruby_version = '>= 2.4'
 
-  spec.files                 = Dir['lib/**/*.rb']
+  spec.files         = Dir['lib/**/*.rb']
   spec.bindir        = 'exe'
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
 
-  spec.add_development_dependency 'bundler', '~> 2.0'
   spec.add_development_dependency 'rake', '~> 10.0'
   spec.add_development_dependency 'rspec', '~> 3.0'
 end