diff --git a/app.py b/app.py
index 5ec0563..22ccaa3 100755
--- a/app.py
+++ b/app.py
@@ -269,8 +269,7 @@ def validate_calibration():
     return redirect('/')
 
 
-@app.route('/download-object/<id>')
-def download_object(id: int):
+def download_object(id: int, tar: archive.ArchiveSender):
     conn = db.get()
     object = db.Object.get_from_id(id, conn).full(conn)
 
@@ -285,8 +284,6 @@ def download_object(id: int):
     ]
 
     # Create archive file to send
-    tar = archive.TarSender()
-
     for calibration_index, (calib, acquisitions) in enumerate(acquisitions_grouped):
         calibration_dir = join(config.CALIBRATION_DIR, str(calib.id))
 
@@ -310,6 +307,16 @@ def download_object(id: int):
     return tar.response()
 
 
+@app.route('/download-object/tar/<id>')
+def download_object_tar(id: int):
+    return download_object(id, archive.TarSender())
+
+
+@app.route('/download-object/zip/<id>')
+def download_object_zip(id: int):
+    return download_object(id, archive.ZipSender())
+
+
 @app.route('/static/<path:path>')
 def send_static(path):
     return send_from_directory('static', path)
diff --git a/archive.py b/archive.py
index a1346b6..3a28610 100644
--- a/archive.py
+++ b/archive.py
@@ -154,7 +154,7 @@ def zip_local_file_header(filename: str, filepath: str, crc: int) -> bytes:
     # Field 11: filename (buffer[30:30+len(filename)])
     buffer[30:30+len(filename)] = filename.encode('ascii')
 
-    return buffer
+    return bytes(buffer)
 
 
 def zip_central_directory_file_header(filename: str, filepath: str, crc: int, offset: int) -> bytes:
@@ -208,7 +208,7 @@ def zip_central_directory_file_header(filename: str, filepath: str, crc: int, of
     # Field 16: filename (buffer[46:46+len(filename)])
     buffer[46:46+len(filename)] = filename.encode('ascii')
 
-    return buffer
+    return bytes(buffer)
 
 
 def zip_end_of_central_directory(items_number: int, central_directory_size: int, central_directory_offset: int):
@@ -230,12 +230,12 @@ def zip_end_of_central_directory(items_number: int, central_directory_size: int,
     buffer[12:16] = central_directory_size.to_bytes(4, byteorder='little')
 
     # Field 7: Offset of start of central directory (buffer[16:20])
-    buffer[16:20] = central_directory_size.to_bytes(4, byteorder='little')
+    buffer[16:20] = central_directory_offset.to_bytes(4, byteorder='little')
 
     # Field 8: Comment length (buffer[20:22])
 
     # Field 9: Comment (buffer[22:])
-    return buffer
+    return bytes(buffer)
 
 
 class ZipSender(ArchiveSender):
diff --git a/templates/object.html b/templates/object.html
index 9366b98..4c33601 100644
--- a/templates/object.html
+++ b/templates/object.html
@@ -4,7 +4,10 @@
 <section class="section">
     <div class="container content">
         <h1 class="title">{{ object.name }}</h1>
-        <a href="/download-object/{{ object.id }}">Télécharger les données de l'objet</a>
+        <div class="my-3">
+            <a class="button is-link mr-3" href="/download-object/tar/{{ object.id }}">Télécharger les données de l'objet (archive TAR)</a>
+            <a class="button is-link" href="/download-object/zip/{{ object.id }}">Télécharger les données de l'objet (archive ZIP)</a>
+        </div>
         {% if object.acquisitions %}
             <div class="fixed-grid has-6-cols">
                 <div class="grid">