diff --git a/.ruby-version b/.ruby-version
index 2bf1c1ccf..8e8299dcc 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-2.3.1
+2.4.2
diff --git a/Dockerfile b/Dockerfile
index 23edadcf1..18eda8d32 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM ruby:2.3.1
+FROM ruby:2.4.2
 RUN apt-get update -qq && apt-get upgrade -y
 
 RUN apt-get install -y build-essential nodejs && apt-get clean
diff --git a/Gemfile b/Gemfile
index 3c631159c..f55d3dbfa 100644
--- a/Gemfile
+++ b/Gemfile
@@ -41,5 +41,5 @@ group :test do
   gem 'capybara'
   gem 'mocha'
   gem 'poltergeist', require: false
-  gem 'webmock', '~> 1.18.0', require: false
+  gem 'webmock', '~> 2.3.0', require: false
 end
diff --git a/Gemfile.lock b/Gemfile.lock
index 5998ed54b..373f626d3 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -130,6 +130,7 @@ GEM
       slimmer (>= 11.1.0)
     govuk_schemas (2.3.0)
       json-schema (~> 2.5.0)
+    hashdiff (0.3.7)
     highline (1.7.8)
     htmlentities (4.3.4)
     http-cookie (1.0.3)
@@ -294,9 +295,10 @@ GEM
       kgio (~> 2.6)
       rack
       raindrops (~> 0.7)
-    webmock (1.18.0)
+    webmock (2.3.2)
       addressable (>= 2.3.6)
       crack (>= 0.3.2)
+      hashdiff
     websocket-driver (0.6.5)
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.2)
@@ -344,11 +346,11 @@ DEPENDENCIES
   slimmer (~> 11.1.0)
   uglifier (>= 1.3.0)
   unicorn (= 4.8)
-  webmock (~> 1.18.0)
+  webmock (~> 2.3.0)
   wraith (~> 4.0)
 
 RUBY VERSION
-   ruby 2.3.1p112
+   ruby 2.4.2p198
 
 BUNDLED WITH
    1.15.3