--- a/trytond/protocols/wrappers.py
+++ b/trytond/protocols/wrappers.py
@@ -12,7 +12,6 @@
     from http import client as HTTPStatus
 
 from werkzeug.wrappers import Request as _Request, Response
-from werkzeug.http import wsgi_to_bytes, bytes_to_wsgi
 from werkzeug.datastructures import Authorization
 from werkzeug.exceptions import abort, HTTPException
 
@@ -113,7 +112,8 @@
 def parse_authorization_header(value):
     if not value:
         return
-    value = wsgi_to_bytes(value)
+    if not isinstance(value, bytes):
+        value = value.encode('latin1')
     try:
         auth_type, auth_info = value.split(None, 1)
         auth_type = auth_type.lower()
@@ -127,9 +127,9 @@
         except Exception:
             return
         return Authorization('session', {
-                'username': bytes_to_wsgi(username),
+                'username': username.decode("latin1"),
                 'userid': userid,
-                'session': bytes_to_wsgi(session),
+                'session': session.decode("latin1"),
                 })
 
 
@@ -214,16 +214,16 @@
             pool = Pool()
             UserApplication = pool.get('res.user.application')
 
-            authorization = wsgi_to_bytes(request.headers['Authorization'])
+            authorization = request.headers['Authorization']
             try:
                 auth_type, auth_info = authorization.split(None, 1)
                 auth_type = auth_type.lower()
             except ValueError:
                 abort(HTTPStatus.UNAUTHORIZED)
-            if auth_type != b'bearer':
+            if auth_type != 'bearer':
                 abort(HTTPStatus.FORBIDDEN)
 
-            application = UserApplication.check(bytes_to_wsgi(auth_info), name)
+            application = UserApplication.check(auth_info, name)
             if not application:
                 abort(HTTPStatus.FORBIDDEN)
             transaction = Transaction()