diff --git a/Gemfile b/Gemfile
index c75764ec..960e1146 100644
--- a/Gemfile
+++ b/Gemfile
@@ -46,7 +46,6 @@ gem 'webpacker'
 gem 'whenever', require: false
 
 # Error Tracing
-gem 'concurrent-ruby'
 gem 'mnemosyne-ruby'
 gem 'newrelic_rpm'
 gem 'sentry-rails'
diff --git a/app/models/submission.rb b/app/models/submission.rb
index b9442084..6bb1cee6 100644
--- a/app/models/submission.rb
+++ b/app/models/submission.rb
@@ -5,8 +5,6 @@ class Submission < ApplicationRecord
   include Creation
   include ActionCableHelper
 
-  require 'concurrent/future'
-
   CAUSES = %w[assess download file render run save submit test autosave requestComments remoteAssess
               remoteSubmit].freeze
   FILENAME_URL_PLACEHOLDER = '{filename}'
diff --git a/lib/docker_client.rb b/lib/docker_client.rb
index cd48721a..313bb226 100644
--- a/lib/docker_client.rb
+++ b/lib/docker_client.rb
@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-require 'concurrent'
 require 'pathname'
 
 class DockerClient
diff --git a/lib/docker_container_pool.rb b/lib/docker_container_pool.rb
index 61de69aa..a89bd461 100644
--- a/lib/docker_container_pool.rb
+++ b/lib/docker_container_pool.rb
@@ -1,8 +1,5 @@
 # frozen_string_literal: true
 
-require 'concurrent/future'
-require 'concurrent/timer_task'
-
 # get_container, destroy_container was moved to lib/runner/strategy/docker_container_pool.rb.
 # return_container is not used anymore because runners are not shared between users anymore.
 # create_container is done by the DockerContainerPool.