diff --git a/Gemfile b/Gemfile
index 321d052ad..832aef7a0 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,7 +9,7 @@ gem "govuk_ab_testing", "~> 2.4"
 gem "govuk_app_config", "~> 2.2"
 gem "govuk_publishing_components", "~> 21.56.1"
 gem "htmlentities", "~> 4.3"
-gem "plek", "~> 3.0"
+gem "plek", "~> 4.0"
 gem "rack_strip_client_ip", "~> 0.0.2"
 gem "rails", "~> 5.2.4"
 gem "rails-controller-testing", "~> 1.0"
diff --git a/Gemfile.lock b/Gemfile.lock
index a5f32a9a1..9aca7c9cc 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -183,7 +183,7 @@ GEM
     parser (2.7.1.3)
       ast (~> 2.4.0)
     phantomjs (2.1.1.0)
-    plek (3.0.0)
+    plek (4.0.0)
     pry (0.13.1)
       coderay (~> 1.1)
       method_source (~> 1.0)
@@ -369,7 +369,7 @@ DEPENDENCIES
   jasmine-rails
   minitest-reporters
   mocha
-  plek (~> 3.0)
+  plek (~> 4.0)
   pry
   rack_strip_client_ip (~> 0.0.2)
   rails (~> 5.2.4)