diff --git a/.gitignore b/.gitignore
index 40f49180..e49dd684 100644
--- a/.gitignore
+++ b/.gitignore
@@ -29,7 +29,6 @@ pickle-email-*.html
 /public/assets
 /bundle
 /doc/app
-.ruby-version
 .vagrant/
 .env
 .env.production
diff --git a/.ruby-version b/.ruby-version
new file mode 100644
index 00000000..437459cd
--- /dev/null
+++ b/.ruby-version
@@ -0,0 +1 @@
+2.5.0
diff --git a/.travis.yml b/.travis.yml
index 11ee8fcc..e8192710 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,7 @@ dist: trusty
 language: ruby
 cache: bundler
 rvm:
-  - 2.4.0@osem --ignore-gemsets
+  - 2.5.0@osem --ignore-gemsets
 branches:
   only:
     - master
diff --git a/Gemfile b/Gemfile
index 355fe038..dfc888c9 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,7 +2,7 @@
 
 source 'https://rubygems.org'
 
-# ruby '2.4'
+ruby ENV['OSEM_RUBY_VERSION'] || '2.5.0'
 
 # rails-assets requires >= 1.8.4
 if Gem::Version.new(Bundler::VERSION) < Gem::Version.new('1.8.4')
diff --git a/Gemfile.lock b/Gemfile.lock
index e846e7b1..e771e026 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -701,5 +701,8 @@ DEPENDENCIES
   webmock
   whenever
 
+RUBY VERSION
+   ruby 2.5.0p0
+
 BUNDLED WITH
    1.16.2
diff --git a/dotenv.example b/dotenv.example
index e2ff2a10..2f4d1da4 100644
--- a/dotenv.example
+++ b/dotenv.example
@@ -83,3 +83,7 @@ RECAPTCHA_SECRET_KEY=""
 
 # The url of the redis server
 OSEM_REDIS_URL='redis://localhost:6379/1'
+
+# The ruby version you want to use with OSEM
+# Please note: We only test 2.5.0
+OSEM_RUBY_VERSION=2.5.0