diff --git a/app/controllers/code_ocean/files_controller.rb b/app/controllers/code_ocean/files_controller.rb
index 34567723..9ceed9cc 100644
--- a/app/controllers/code_ocean/files_controller.rb
+++ b/app/controllers/code_ocean/files_controller.rb
@@ -23,7 +23,7 @@ module CodeOcean
       raise Pundit::NotAuthorizedError if @embed_options[:disable_download] || @file.filepath != params[:filename]
 
       real_location = Pathname(@file.native_file.current_path).realpath
-      send_file(real_location, type: @file.native_file.content_type, filename: @file.name_with_extension, disposition: 'attachment')
+      send_file(real_location, type: 'application/octet-stream', filename: @file.name_with_extension, disposition: 'attachment')
     end
 
     def render_protected_upload
diff --git a/app/controllers/submissions_controller.rb b/app/controllers/submissions_controller.rb
index 229aec47..bb9e49b7 100644
--- a/app/controllers/submissions_controller.rb
+++ b/app/controllers/submissions_controller.rb
@@ -57,7 +57,7 @@ class SubmissionsController < ApplicationController
     end
     zip_data = stringio.string
     response.set_header('Content-Length', zip_data.size)
-    send_data(zip_data, filename: "#{@submission.exercise.title.tr(' ', '_')}.zip")
+    send_data(zip_data, type: 'application/octet-stream', filename: "#{@submission.exercise.title.tr(' ', '_')}.zip", disposition: 'attachment')
   end
 
   def download_file
@@ -67,7 +67,7 @@ class SubmissionsController < ApplicationController
       redirect_to protected_upload_path(id: @file.id, filename: @file.filepath)
     else
       response.set_header('Content-Length', @file.size)
-      send_data(@file.content, filename: @file.name_with_extension, disposition: 'attachment')
+      send_data(@file.content, type: 'application/octet-stream', filename: @file.name_with_extension, disposition: 'attachment')
     end
   end
 
diff --git a/spec/controllers/code_ocean/files_controller_spec.rb b/spec/controllers/code_ocean/files_controller_spec.rb
index 476b72bc..41f042d9 100644
--- a/spec/controllers/code_ocean/files_controller_spec.rb
+++ b/spec/controllers/code_ocean/files_controller_spec.rb
@@ -17,7 +17,7 @@ describe CodeOcean::FilesController do
         let(:file) { submission.collect_files.detect {|file| file.file_type.file_extension == '.mp4' } }
 
         expect_assigns(file: :file)
-        expect_content_type('video/mp4')
+        expect_content_type('application/octet-stream')
         expect_http_status(:ok)
 
         it 'sets the correct filename' do
diff --git a/spec/controllers/submissions_controller_spec.rb b/spec/controllers/submissions_controller_spec.rb
index afdaa088..ed33a37f 100644
--- a/spec/controllers/submissions_controller_spec.rb
+++ b/spec/controllers/submissions_controller_spec.rb
@@ -85,7 +85,7 @@ describe SubmissionsController do
 
         expect_assigns(file: :file)
         expect_assigns(submission: :submission)
-        expect_content_type('text/javascript')
+        expect_content_type('application/octet-stream')
         expect_http_status(:ok)
 
         it 'sets the correct filename' do