diff --git a/Gemfile b/Gemfile
index 6e8adcbc..cad0b7cf 100644
--- a/Gemfile
+++ b/Gemfile
@@ -42,7 +42,7 @@ gem 'sass-rails'
 gem 'slim-rails'
 gem 'sorcery' # Causes a deprecation warning in Rails 6.0+, see: https://github.com/Sorcery/sorcery/pull/255
 gem 'telegraf'
-gem 'tubesock', github: 'gosukiwi/tubesock', branch: 'patch-1' # Switch to a fork which is compatible with Rails 5
+gem 'tubesock'
 gem 'turbolinks'
 gem 'webpacker'
 gem 'whenever', require: false
diff --git a/Gemfile.lock b/Gemfile.lock
index 39c110b1..a5356d11 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -6,15 +6,6 @@ GIT
       json (~> 2.6.1)
       structured_warnings (~> 0.4.0)
 
-GIT
-  remote: https://github.com/gosukiwi/tubesock.git
-  revision: 86a5ca4f7d3c3a7b9a727ad91df3b9b4912eda39
-  branch: patch-1
-  specs:
-    tubesock (0.2.7)
-      rack (>= 1.5.0)
-      websocket (>= 1.1.0)
-
 GIT
   remote: https://github.com/openHPI/proforma.git
   revision: dc68000325388e1d75f31be9e136a82edad8a56d
@@ -162,7 +153,7 @@ GEM
       regexp_parser (~> 2.2)
     erubi (1.10.0)
     eventmachine (1.2.7)
-    excon (0.92.1)
+    excon (0.92.2)
     factory_bot (6.2.1)
       activesupport (>= 5.0.0)
     factory_bot_rails (6.2.0)
@@ -238,7 +229,7 @@ GEM
     listen (3.7.1)
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
-    loofah (2.15.0)
+    loofah (2.16.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)
@@ -264,7 +255,7 @@ GEM
     mnemosyne-ruby (1.12.1)
       activesupport (>= 4)
       bunny
-    msgpack (1.4.5)
+    msgpack (1.5.1)
     multi_json (1.15.0)
     multi_xml (0.6.0)
     nested_form (0.3.2)
@@ -287,7 +278,7 @@ GEM
       rack (>= 1.2, < 3)
     pagedown-bootstrap-rails (2.1.4)
       railties (> 3.1)
-    parallel (1.22.0)
+    parallel (1.22.1)
     parser (3.1.1.0)
       ast (~> 2.4.1)
     path_expander (1.1.0)
@@ -397,7 +388,7 @@ GEM
     rspec-expectations (3.11.0)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.11.0)
-    rspec-mocks (3.11.0)
+    rspec-mocks (3.11.1)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.11.0)
     rspec-rails (5.1.1)
@@ -495,6 +486,9 @@ GEM
     temple (0.8.2)
     thor (1.2.1)
     tilt (2.0.10)
+    tubesock (0.2.9)
+      rack (>= 1.5.0)
+      websocket (>= 1.1.0)
     turbolinks (5.2.1)
       turbolinks-source (~> 5.2)
     turbolinks-source (5.2.0)
@@ -603,7 +597,7 @@ DEPENDENCIES
   sorcery
   spring
   telegraf
-  tubesock!
+  tubesock
   turbolinks
   web-console
   webmock
diff --git a/app/controllers/submissions_controller.rb b/app/controllers/submissions_controller.rb
index c1e6418b..83fefdb4 100644
--- a/app/controllers/submissions_controller.rb
+++ b/app/controllers/submissions_controller.rb
@@ -85,7 +85,10 @@ class SubmissionsController < ApplicationController
 
     hijack do |tubesock|
       client_socket = tubesock
-      return kill_client_socket(client_socket) if @embed_options[:disable_run]
+
+      client_socket.onopen do |_event|
+        kill_client_socket(client_socket) if @embed_options[:disable_run]
+      end
 
       client_socket.onclose do |_event|
         runner_socket&.close(:terminated_by_client)
@@ -177,16 +180,18 @@ class SubmissionsController < ApplicationController
 
   def score
     hijack do |tubesock|
-      return if @embed_options[:disable_score]
+      tubesock.onopen do |_event|
+        kill_client_socket(tubesock) if @embed_options[:disable_score]
 
-      tubesock.send_data(JSON.dump(@submission.calculate_score))
-      # To enable hints when scoring a submission, uncomment the next line:
-      # send_hints(tubesock, StructuredError.where(submission: @submission))
+        tubesock.send_data(JSON.dump(@submission.calculate_score))
+        # To enable hints when scoring a submission, uncomment the next line:
+        # send_hints(tubesock, StructuredError.where(submission: @submission))
+        kill_client_socket(tubesock)
+      end
     rescue Runner::Error => e
       tubesock.send_data JSON.dump({cmd: :status, status: :container_depleted})
-      Rails.logger.debug { "Runner error while scoring submission #{@submission.id}: #{e.message}" }
-    ensure
       kill_client_socket(tubesock)
+      Rails.logger.debug { "Runner error while scoring submission #{@submission.id}: #{e.message}" }
     end
   end
 
@@ -196,14 +201,16 @@ class SubmissionsController < ApplicationController
 
   def test
     hijack do |tubesock|
-      return kill_client_socket(tubesock) if @embed_options[:disable_run]
+      tubesock.onopen do |_event|
+        kill_client_socket(tubesock) if @embed_options[:disable_run]
 
-      tubesock.send_data(JSON.dump(@submission.test(@file)))
+        tubesock.send_data(JSON.dump(@submission.test(@file)))
+        kill_client_socket(tubesock)
+      end
     rescue Runner::Error => e
       tubesock.send_data JSON.dump({cmd: :status, status: :container_depleted})
-      Rails.logger.debug { "Runner error while testing submission #{@submission.id}: #{e.message}" }
-    ensure
       kill_client_socket(tubesock)
+      Rails.logger.debug { "Runner error while testing submission #{@submission.id}: #{e.message}" }
     end
   end