diff --git a/.travis.yml b/.travis.yml
index e96dc3f..ca82c3d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,4 @@
 language: ruby
 rvm:
-  - 2.4.0
   - 2.3.3
-  - 2.2.4
-  - 2.1.10
 cache: bundler
diff --git a/Gemfile b/Gemfile
index f28bd78..6beb90b 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,5 +1,7 @@
 source 'https://rubygems.org'
 
+ruby "2.3.3"
+
 gem 'rake'
 gem 'thor'
 gem 'puma'
diff --git a/Gemfile.lock b/Gemfile.lock
index 73a58bd..4b5b55e 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -53,5 +53,8 @@ DEPENDENCIES
   rspec
   thor
 
+RUBY VERSION
+   ruby 2.3.3p222
+
 BUNDLED WITH
    1.14.3