diff --git a/app/lib/active_storage/downloadable_file.rb b/app/lib/active_storage/downloadable_file.rb
index 8af799df4..914ca478d 100644
--- a/app/lib/active_storage/downloadable_file.rb
+++ b/app/lib/active_storage/downloadable_file.rb
@@ -24,11 +24,14 @@ class ActiveStorage::DownloadableFile
   private
 
   def self.timestamped_filename(piece_justificative)
+    # we pad the original file name with a timestamp
+    # and a short id in order to help identify multiple versions and avoid name collisions
     extension = File.extname(piece_justificative.filename.to_s)
     basename = File.basename(piece_justificative.filename.to_s, extension)
-    timestamp = piece_justificative.created_at.strftime("%d-%m-%Y-%H-%S")
+    timestamp = piece_justificative.created_at.strftime("%d-%m-%Y-%H-%M")
+    id = piece_justificative.id % 10000
 
-    "#{basename}-#{timestamp}#{extension}"
+    "#{basename}-#{timestamp}-#{id}#{extension}"
   end
 
   def using_local_backend?
diff --git a/spec/features/instructeurs/instruction_spec.rb b/spec/features/instructeurs/instruction_spec.rb
index 2b03cfa8c..7a7c8fdd5 100644
--- a/spec/features/instructeurs/instruction_spec.rb
+++ b/spec/features/instructeurs/instruction_spec.rb
@@ -138,6 +138,55 @@ feature 'Instructing a dossier:' do
     expect(page).to have_text("Dossier envoyé")
   end
 
+  context 'A instructeur can download a zip of the attachments of a dossier', js: true do
+    let(:procedure) { create(:procedure, :published, :with_piece_justificative, instructeurs: [instructeur]) }
+    let(:dossier) { create(:dossier, :en_construction, procedure: procedure) }
+    let(:champ) { dossier.champs.first }
+    let(:path) { 'spec/fixtures/files/piece_justificative_0.pdf' }
+    let(:commentaire) { create(:commentaire, instructeur: instructeur, dossier: dossier) }
+
+    before {
+      champ.piece_justificative_file.attach(io: File.open(path), filename: "piece_justificative_0.pdf", content_type: "application/pdf")
+
+      log_in(instructeur.email, password)
+      visit instructeur_dossier_path(procedure, dossier)
+    }
+
+    scenario 'it possible to open the zip file' do
+      find(:css, '.attached').click
+      click_on 'Télécharger toutes les pièces jointes'
+      # For some reason, clicking the download link does not trigger the download in the headless browser ;
+      # So we need to go to the download link directly
+      visit telecharger_pjs_instructeur_dossier_path(procedure, dossier)
+
+      DownloadHelpers.wait_for_download
+      files = ZipTricks::FileReader.read_zip_structure(io: File.open(DownloadHelpers.download))
+
+      expect(DownloadHelpers.download).to include "dossier-#{dossier.id}.zip"
+      expect(files.size).to be 1
+      expect(files[0].filename.include?('piece_justificative_0')).to be_truthy
+      expect(files[0].uncompressed_size).to be File.size(path)
+    end
+
+    scenario 'it possible to open the zip file with multiple attachments' do
+      commentaire.piece_jointe.attach(io: File.open(path), filename: "piece_justificative_0.pdf", content_type: "application/pdf")
+
+      visit telecharger_pjs_instructeur_dossier_path(procedure, dossier)
+      DownloadHelpers.wait_for_download
+      files = ZipTricks::FileReader.read_zip_structure(io: File.open(DownloadHelpers.download))
+
+      expect(DownloadHelpers.download).to include "dossier-#{dossier.id}.zip"
+      expect(files.size).to be 2
+      expect(files[0].filename.include?('piece_justificative_0')).to be_truthy
+      expect(files[1].filename.include?('piece_justificative_0')).to be_truthy
+      expect(files[0].filename).not_to eq files[1].filename
+      expect(files[0].uncompressed_size).to be File.size(path)
+      expect(files[1].uncompressed_size).to be File.size(path)
+    end
+
+    after { DownloadHelpers.clear_downloads }
+  end
+
   def log_in(email, password, check_email: true)
     visit '/'
     click_on 'Connexion'
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 8d9099c30..80723180c 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -45,10 +45,19 @@ Capybara.register_driver :headless_chrome do |app|
     chromeOptions: { args: ['disable-dev-shm-usage', 'disable-software-rasterizer', 'mute-audio', 'window-size=1440,900'] }
   )
 
-  Capybara::Selenium::Driver.new app,
+  download_path = Capybara.save_path
+  # Chromedriver 77 requires setting this for headless mode on linux
+  # Different versions of Chrome/selenium-webdriver require setting differently - jus set them all
+  options.add_preference('download.default_directory', download_path)
+  options.add_preference(:download, default_directory: download_path)
+
+  Capybara::Selenium::Driver.new(app,
     browser: :chrome,
     desired_capabilities: capabilities,
-    options: options
+    options: options).tap do |driver|
+    # Set download dir for Chrome < 77
+    driver.browser.download_path = download_path
+  end
 end
 
 # FIXME: remove this line when https://github.com/rspec/rspec-rails/issues/1897 has been fixed
diff --git a/spec/support/download_helpers.rb b/spec/support/download_helpers.rb
new file mode 100644
index 000000000..1515adaec
--- /dev/null
+++ b/spec/support/download_helpers.rb
@@ -0,0 +1,36 @@
+module DownloadHelpers
+  TIMEOUT = 2
+
+  extend self
+
+  def downloads
+    Dir[Capybara.save_path.join("*.zip")]
+  end
+
+  def download
+    downloads.first
+  end
+
+  def download_content
+    wait_for_download
+    File.read(download)
+  end
+
+  def wait_for_download
+    Timeout.timeout(TIMEOUT) do
+      sleep 0.1 until downloaded?
+    end
+  end
+
+  def downloaded?
+    !downloading? && downloads.any?
+  end
+
+  def downloading?
+    downloads.grep(/\.part$/).any?
+  end
+
+  def clear_downloads
+    FileUtils.rm_f(downloads)
+  end
+end