diff --git a/Gemfile.lock b/Gemfile.lock
index 015d9f0..e91b581 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,30 +1,30 @@
 PATH
   remote: .
   specs:
-    deb-s3 (0.11.2)
+    deb-s3 (0.11.4)
       aws-sdk-s3 (~> 1)
       thor (~> 0.19.0)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    aws-eventstream (1.1.1)
-    aws-partitions (1.442.0)
-    aws-sdk-core (3.113.1)
+    aws-eventstream (1.2.0)
+    aws-partitions (1.574.0)
+    aws-sdk-core (3.130.0)
       aws-eventstream (~> 1, >= 1.0.2)
-      aws-partitions (~> 1, >= 1.239.0)
+      aws-partitions (~> 1, >= 1.525.0)
       aws-sigv4 (~> 1.1)
       jmespath (~> 1.0)
-    aws-sdk-kms (1.43.0)
-      aws-sdk-core (~> 3, >= 3.112.0)
+    aws-sdk-kms (1.55.0)
+      aws-sdk-core (~> 3, >= 3.127.0)
       aws-sigv4 (~> 1.1)
-    aws-sdk-s3 (1.93.0)
-      aws-sdk-core (~> 3, >= 3.112.0)
+    aws-sdk-s3 (1.113.0)
+      aws-sdk-core (~> 3, >= 3.127.0)
       aws-sdk-kms (~> 1)
-      aws-sigv4 (~> 1.1)
-    aws-sigv4 (1.2.3)
+      aws-sigv4 (~> 1.4)
+    aws-sigv4 (1.4.0)
       aws-eventstream (~> 1, >= 1.0.2)
-    jmespath (1.4.0)
+    jmespath (1.6.1)
     minitest (5.14.4)
     rake (13.0.3)
     thor (0.19.4)
diff --git a/lib/deb/s3/cli.rb b/lib/deb/s3/cli.rb
index e6802ff..9096306 100644
--- a/lib/deb/s3/cli.rb
+++ b/lib/deb/s3/cli.rb
@@ -243,33 +243,46 @@ def upload(*files)
         end
       end
 
+      # Remember which files were moved to temporary filenames
+      filenames_to_move = []
+      log_action = lambda {|f| sublog("Transferring #{f}") }
+      atomic_action = lambda {|f|
+        log_action.call(f)
+        filenames_to_move.append(f)
+      }
+
       # upload the manifest
       log("Uploading new manifests to S3")
       manifests.each_value do |manifest|
         begin
-          manifest.write_manifests_to_s3 { |f| sublog("Transferring #{f}") }
+          manifest.write_manifests_to_s3 &log_action
         rescue Deb::S3::Utils::AlreadyExistsError => e
           error("Uploading manifest failed because: #{e}")
         end
         release.update_manifest(manifest)
       end
-      release.write_to_s3 { |f| sublog("Transferring #{f}") }
-
+      release.write_to_s3 &log_action
       # release the lock and upload the packages (assuming their names are unique)
       if options[:lock] && @lock_acquired
         Deb::S3::Lock.unlock(options[:codename], component, options[:arch], options[:cache_control])
         log("Lock released.")
         early_release = true
       end
-      log("Uploading packages to S3")
+      log("Uploading packages to S3 as temporary files")
       manifests.each_value do |manifest|
         begin
-          manifest.write_packages_to_s3 { |f| sublog("Transferring #{f}") }
+          manifest.write_packages_to_s3 &atomic_action
         rescue Deb::S3::Utils::AlreadyExistsError => e
           error("Uploading manifest failed because: #{e}")
         end
       end
 
+      log("Moving temporary files to their final paths")
+      filenames_to_move.each do |f|
+        sublog("Moving #{f}")
+        Deb::S3::Utils.s3_finish_atomic_store(f)
+      end
+
       log("Update complete.")
     ensure
       if !early_release && options[:lock] && @lock_acquired
diff --git a/lib/deb/s3/manifest.rb b/lib/deb/s3/manifest.rb
index 1bbf0c2..d324864 100644
--- a/lib/deb/s3/manifest.rb
+++ b/lib/deb/s3/manifest.rb
@@ -104,7 +104,7 @@ def write_packages_to_s3
       # store any packages that need to be stored
       @packages_to_be_upload.each do |pkg|
         yield pkg.url_filename(@codename) if block_given?
-        s3_store(pkg.filename, pkg.url_filename(@codename), 'application/octet-stream; charset=binary', self.cache_control, self.fail_if_exists)
+        s3_atomic_store(pkg.filename, pkg.url_filename(@codename), 'application/octet-stream; charset=binary', self.cache_control, self.fail_if_exists)
       end
     end
   end
diff --git a/lib/deb/s3/utils.rb b/lib/deb/s3/utils.rb
index 5ae06cf..2c8b2c4 100644
--- a/lib/deb/s3/utils.rb
+++ b/lib/deb/s3/utils.rb
@@ -106,6 +106,36 @@ def s3_store(path, filename=nil, content_type='application/octet-stream; charset
     end
   end
 
+  # Similar to s3_store, but uploads the file with a temporary filename instead,
+  # so the object is not visible with its final filename while being uploaded. 
+  # The files then need to be moved to their actual filename with
+  # s3_finish_atomic_store
+  def s3_atomic_store(path, filename=nil, content_type='application/octet-stream; charset=binary', cache_control=nil, fail_if_exists=false, suffix=".deb-s3-temp")
+    filename = File.basename(path) unless filename
+    # TODO: check that the filename does not exist
+    temp_filename = filename + suffix
+    s3_store(path, filename=temp_filename, content_type, cache_control, fail_if_exists)
+  end
+
+  # See s3_atomic_store
+  def s3_finish_atomic_store(filename, suffix=".deb-s3-temp")
+    temp_filename = filename + suffix
+    # Can only copy up to 5 Gb files
+    s3_copy(temp_filename, filename)
+    # There is no move is S3, only copy then delete.
+    s3_remove(temp_filename) 
+  end
+
+  def s3_copy(filename_from, filename_to)
+    full_from_path = Deb::S3::Utils.bucket + "/" + s3_path(filename_from)
+    Deb::S3::Utils.s3.copy_object(
+      :bucket => Deb::S3::Utils.bucket,
+      :acl => Deb::S3::Utils.access_policy,
+      :copy_source => full_from_path,
+      :key => s3_path(filename_to)
+    )
+  end
+
   def s3_remove(path)
     if s3_exists?(path)
       Deb::S3::Utils.s3.delete_object(