diff --git a/config/initializers/logstasher.rb b/config/initializers/logstasher.rb
new file mode 100644
index 000000000..36e2f1b8b
--- /dev/null
+++ b/config/initializers/logstasher.rb
@@ -0,0 +1,5 @@
+if Object.const_defined?('LogStasher') && LogStasher.enabled
+  LogStasher.add_custom_fields do |fields|
+    fields[:govuk_content_pages_variant] = request.headers['GOVUK-ABTest-ContentPagesNav']
+  end
+end