diff --git a/Gemfile b/Gemfile
index 4007203..dae5e50 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,3 +1,4 @@
+ruby '>=2.3.1'
 source 'https://rubygems.org'
 
 # Middleman
diff --git a/Gemfile.lock b/Gemfile.lock
index 22eeabf..1fc04a9 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -122,5 +122,8 @@ DEPENDENCIES
   redcarpet (~> 3.4.0)
   rouge (~> 2.0.5)
 
+RUBY VERSION
+   ruby 2.3.3p222
+
 BUNDLED WITH
    1.14.5
diff --git a/README.md b/README.md
index b685fc6..f08186c 100644
--- a/README.md
+++ b/README.md
@@ -37,7 +37,7 @@ Getting Started with Slate
 You're going to need:
 
  - **Linux or OS X** — Windows may work, but is unsupported.
- - **Ruby, version 2.2.5 or newer**
+ - **Ruby, version 2.3.1 or newer**
  - **Bundler** — If Ruby is already installed, but the `bundle` command doesn't work, just run `gem install bundler` in a terminal.
 
 ### Getting Set Up