diff --git a/trytond/modules/__init__.py b/trytond/modules/__init__.py
index 718a441e6f..c8a43af86b 100644
--- a/trytond/modules/__init__.py
+++ b/trytond/modules/__init__.py
@@ -244,7 +244,7 @@ def load_module_graph(graph, pool, update=None, lang=None):
                 filename = filename.replace('/', os.sep)
                 logger.info('%s:loading %s', module, filename)
                 # Feed the parser with xml content:
-                with tools.file_open(OPJ(module, filename)) as fp:
+                with tools.file_open(OPJ(module, filename), 'rb') as fp:
                     tryton_parser.parse_xmlstream(fp)
 
             modules_todo.append((module, list(tryton_parser.to_delete)))
diff --git a/trytond/tools/misc.py b/trytond/tools/misc.py
index f9dfb87e0c..a41c8822be 100644
--- a/trytond/tools/misc.py
+++ b/trytond/tools/misc.py
@@ -51,7 +51,7 @@ def exec_command_pipe(name, *args, **kwargs):
         stdout=subprocess.PIPE, env=child_env)
 
 
-def file_open(name, mode="r", subdir='modules', encoding='utf-8'):
+def file_open(name, mode="r", subdir='modules', encoding=None):
     """Open a file from the root dir, using a subdir folder."""
     from trytond.modules import EGG_MODULES
     if sys.version_info < (3,):