diff --git a/app/controllers/submissions_controller.rb b/app/controllers/submissions_controller.rb
index d6a92055..bc3ec4a6 100644
--- a/app/controllers/submissions_controller.rb
+++ b/app/controllers/submissions_controller.rb
@@ -122,7 +122,7 @@ class SubmissionsController < ApplicationController
   def run
     # TODO reimplement SSEs with websocket commands
     # with_server_sent_events do |server_sent_event|
-    #   output = @docker_client.execute_run_command(@submission, params[:filename])
+    #   output = @docker_client.execute_run_command(@submission, sanitize_filename)
 
     #   server_sent_event.write({stdout: output[:stdout]}, event: 'output') if output[:stdout]
     #   server_sent_event.write({stderr: output[:stderr]}, event: 'output') if output[:stderr]
@@ -147,7 +147,7 @@ class SubmissionsController < ApplicationController
       # give the docker_client the tubesock object, so that it can send messages (timeout)
       @docker_client.tubesock = tubesock
 
-      result = @docker_client.execute_run_command(@submission, params[:filename])
+      result = @docker_client.execute_run_command(@submission, sanitize_filename)
       tubesock.send_data JSON.dump({'cmd' => 'status', 'status' => result[:status]})
 
       if result[:status] == :container_running
@@ -200,6 +200,10 @@ class SubmissionsController < ApplicationController
     # save the output of this "run" as a "testrun" (scoring runs are saved in submission_scoring.rb)
     save_run_output
 
+    if @run_output.blank?
+      parse_message t('exercises.implement.no_output', timestamp: l(Time.now, format: :short)), 'stdout', tubesock
+    end
+
     # Hijacked connection needs to be notified correctly
     tubesock.send_data JSON.dump({'cmd' => 'exit'})
     tubesock.close
@@ -219,8 +223,8 @@ class SubmissionsController < ApplicationController
       @run_output = 'timeout: ' + @run_output # add information that this run timed out to the buffer
     else
       # Filter out information about run_command, test_command, user or working directory
-      run_command = @submission.execution_environment.run_command % command_substitutions(params[:filename])
-      test_command = @submission.execution_environment.test_command % command_substitutions(params[:filename])
+      run_command = @submission.execution_environment.run_command % command_substitutions(sanitize_filename)
+      test_command = @submission.execution_environment.test_command % command_substitutions(sanitize_filename)
       unless /root|workspace|#{run_command}|#{test_command}/.match(message)
         parse_message(message, 'stdout', tubesock)
       end
@@ -331,7 +335,7 @@ class SubmissionsController < ApplicationController
   private :set_docker_client
 
   def set_file
-    @file = @files.detect { |file| file.name_with_extension == params[:filename] }
+    @file = @files.detect { |file| file.name_with_extension == sanitize_filename }
     head :not_found unless @file
   end
   private :set_file
@@ -372,7 +376,7 @@ class SubmissionsController < ApplicationController
     hijack do |tubesock|
       Thread.new { EventMachine.run } unless EventMachine.reactor_running? && EventMachine.reactor_thread.alive?
 
-      output = @docker_client.execute_test_command(@submission, params[:filename])
+      output = @docker_client.execute_test_command(@submission, sanitize_filename)
 
       # tubesock is the socket to the client
       tubesock.send_data JSON.dump(output)
@@ -416,4 +420,8 @@ class SubmissionsController < ApplicationController
     end
     path
   end
+
+  def sanitize_filename
+    params[:filename].gsub(/\.json$/, '')
+  end
 end
diff --git a/app/views/execution_environments/shell.html.slim b/app/views/execution_environments/shell.html.slim
index 5b499a35..ae35c7b8 100644
--- a/app/views/execution_environments/shell.html.slim
+++ b/app/views/execution_environments/shell.html.slim
@@ -4,5 +4,5 @@ h1 = @execution_environment
   .form-group
     label for='command' = t('.command')
     input#command.form-control type='text'
-  pre#output data-message-no-output=t('exercises.implement.no_output')
+  pre#output data-message-no-output=t('exercises.implement.no_output', timestamp: l(Time.now, format: :short))
     p = t('exercises.implement.no_output_yet')
diff --git a/app/views/exercises/_editor_output.html.slim b/app/views/exercises/_editor_output.html.slim
index 91f289d8..7948e548 100644
--- a/app/views/exercises/_editor_output.html.slim
+++ b/app/views/exercises/_editor_output.html.slim
@@ -1,6 +1,6 @@
 div id='output_sidebar_collapsed'
   = render('editor_button', classes: 'btn-block btn-primary btn', data: {:'data-toggle' => 'tooltip', :'data-placement' => 'left'}, title: t('exercises.editor.expand_output_sidebar'), icon: 'fa fa-plus-square', id: 'toggle-sidebar-output-collapsed', label: '')
-div.h-100 id='output_sidebar_uncollapsed' class='d-none col-sm-12 enforce-bottom-margin' data-message-no-output=t('exercises.implement.no_output')
+div.h-100 id='output_sidebar_uncollapsed' class='d-none col-sm-12 enforce-bottom-margin' data-message-no-output=t('exercises.implement.no_output_yet')
   .row
     = render('editor_button', classes: 'btn-block btn-primary btn', icon: 'fa fa-minus-square', id: 'toggle-sidebar-output', label: t('exercises.editor.collapse_output_sidebar'))
 
diff --git a/config/locales/de.yml b/config/locales/de.yml
index 4cbd120c..f385a3d3 100644
--- a/config/locales/de.yml
+++ b/config/locales/de.yml
@@ -300,7 +300,7 @@ de:
       file: 'Test-Datei <span class="number">%{number}</span> (<span class="filename">%{filename}</span>)'
       hint: Tipp
       no_files: Die Aufgabe umfasst noch keine sichtbaren Dateien.
-      no_output: Die letzte Code-Ausführung hat keine Ausgabe erzeugt.
+      no_output: Die letzte Code-Ausführung terminierte am %{timestamp} ohne Ausgabe.
       no_output_yet: Bisher existiert noch keine Ausgabe.
       output: Programm-Ausgabe
       passed_tests: Erfolgreiche Tests
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 40922a02..0bcfd014 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -300,7 +300,7 @@ en:
       file: 'Test File <span class="number">%{number}</span> (<span class="filename">%{filename}</span>)'
       hint: Hint
       no_files: The exercise does not comprise visible files yet.
-      no_output: The last code run has not generated any output.
+      no_output: The last code run finished on %{timestamp} without any output.
       no_output_yet: There is no output yet.
       output: Program Output
       passed_tests: Passed Tests