diff --git a/grandlyon_cartads_cs/models.py b/grandlyon_cartads_cs/models.py
index c70fe52..16786f0 100644
--- a/grandlyon_cartads_cs/models.py
+++ b/grandlyon_cartads_cs/models.py
@@ -85,13 +85,13 @@ class GLCartaDSCS(AbstractCartaDSCS):
         return token
 
     def upload_zip(self, zip_filename):
-        b64_zip = base64.b64encode(open(zip_filename).read())
+        b64_zip = base64.b64encode(open(zip_filename, 'rb').read())
         chunk_size = 16777216  # 16MB
         for n in range(0, len(b64_zip), chunk_size):
             resp = self.requests.post(self.sendfile_ws_url,
                     data={
                         'fileName': self.sendfile_ws_dirname + os.path.basename(zip_filename),
-                        'b64_fileContent': b64_zip[n:n+chunk_size],
+                        'b64_fileContent': b64_zip[n:n+chunk_size].decode('ascii'),
                     }
                     )
             resp.raise_for_status()