diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index f4a97638a9..c6711bb01a 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -410,6 +410,6 @@ jobs:
           include-hidden-files: true
       - name: Compare SimpleCov results with Undercover
         run: |
-          git fetch --no-tags origin master:master
+          git fetch --no-tags origin ${{ github.event.pull_request.base.ref }}:master
           bundle exec undercover
         if: ${{ github.ref != 'refs/heads/master' }} # Does not run on master, as we can't fetch master in the master branch
diff --git a/.rubocop_styleguide.yml b/.rubocop_styleguide.yml
index b82dbada1e..91c745cdd9 100644
--- a/.rubocop_styleguide.yml
+++ b/.rubocop_styleguide.yml
@@ -16,6 +16,7 @@ AllCops:
     - node_modules/**/*
     # Excluding: inadequate Naming/FileName rule rejects GemFile name with camelcase
     - engines/web/Gemfile
+    - .undercover
 
 Bundler/DuplicatedGem:
   Enabled: false
diff --git a/.simplecov b/.simplecov
index 66573a094d..dd47f33e21 100755
--- a/.simplecov
+++ b/.simplecov
@@ -4,17 +4,11 @@
 SimpleCov.start 'rails' do
   add_filter '/bin/'
   add_filter '/config/'
-  add_filter '/jobs/application_job.rb'
-  add_filter '/schemas/'
-  add_filter '/lib/generators'
-  add_filter '/spec/'
-  add_filter '/vendor/'
-  add_filter '/public'
-  add_filter '/swagger'
   add_filter '/script'
-  add_filter '/log'
   add_filter '/db'
-  add_filter '/lib/tasks/sample_data/'
+
+  # We haven't managed to make simplecov recognise rake coverage accurately.
+  add_filter '/lib/tasks/'
 
   formatter SimpleCov::Formatter::SimpleFormatter
 end
diff --git a/.undercover b/.undercover
index 95a9fe08c9..9b7d04fdb9 100644
--- a/.undercover
+++ b/.undercover
@@ -1,5 +1,4 @@
 #!/bin/env ruby
 # frozen_string_literal: true
 
--l coverage/lcov/openfoodnetwork.lcov
--c master
\ No newline at end of file
+-c master
diff --git a/Gemfile b/Gemfile
index a80dab5fe4..fd77f79d72 100644
--- a/Gemfile
+++ b/Gemfile
@@ -174,7 +174,6 @@ group :test do
   gem 'puffing-billy'
   gem 'rails-controller-testing'
   gem 'simplecov', require: false
-  gem 'simplecov-lcov', require: false
   gem 'undercover', require: false
   gem 'vcr', require: false
   gem 'webmock', require: false
diff --git a/Gemfile.lock b/Gemfile.lock
index b42743cb50..6c1600ba7d 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -769,7 +769,6 @@ GEM
       simplecov-html (~> 0.11)
       simplecov_json_formatter (~> 0.1)
     simplecov-html (0.12.3)
-    simplecov-lcov (0.8.0)
     simplecov_json_formatter (0.1.4)
     spreadsheet_architect (5.0.0)
       caxlsx (>= 3.3.0, < 4)
@@ -1016,7 +1015,6 @@ DEPENDENCIES
   sidekiq
   sidekiq-scheduler
   simplecov
-  simplecov-lcov
   spreadsheet_architect
   spring
   spring-commands-rspec
diff --git a/lib/tasks/simplecov.rake b/lib/tasks/simplecov.rake
index d5bc344f06..cc7f5c95e6 100644
--- a/lib/tasks/simplecov.rake
+++ b/lib/tasks/simplecov.rake
@@ -5,7 +5,7 @@ namespace :simplecov do
   task :collate_results, # rubocop:disable Rails/RakeEnvironment doesn't need the full env
        [:path_to_results, :coverage_dir] do |_t, args|
     require "simplecov"
-    require "simplecov-lcov"
+    require "undercover/simplecov_formatter"
 
     path_to_results = args[:path_to_results].presence || "tmp/simplecov"
     output_path = args[:coverage_dir].presence || "coverage"
@@ -15,9 +15,8 @@ namespace :simplecov do
       coverage_dir(output_path)
     end
 
-    SimpleCov::Formatter::LcovFormatter.config.report_with_single_file = true
     SimpleCov.collate Dir[File.join(path_to_results, "**", ".resultset.json")], "rails" do
-      formatter(SimpleCov::Formatter::LcovFormatter)
+      formatter(SimpleCov::Formatter::Undercover)
       coverage_dir(output_path)
     end
   end
diff --git a/spec/lib/tasks/simplecov_spec.rb b/spec/lib/tasks/simplecov_spec.rb
index 68e9d0bc5e..62204b12ef 100644
--- a/spec/lib/tasks/simplecov_spec.rb
+++ b/spec/lib/tasks/simplecov_spec.rb
@@ -26,6 +26,10 @@ RSpec.describe "simplecov.rake" do
 
             and change { File.exist?(File.join(output_dir, "index.html")) }.
             from(false).
+            to(true).
+
+            and change { File.exist?(File.join(output_dir, "coverage.json")) }.
+            from(false).
             to(true)
         end
       end