diff --git a/trytond/trytond/filestore.py b/trytond/trytond/filestore.py
index 814643bfae..fa08aaca9b 100644
--- a/trytond/trytond/filestore.py
+++ b/trytond/trytond/filestore.py
@@ -8,6 +8,8 @@ from trytond.tools import resolve
 
 __all__ = ['filestore']
 
+PATH = os.path.normpath(config.get('database', 'path'))
+
 
 class FileStore(object):
 
@@ -51,10 +53,9 @@ class FileStore(object):
         return [self.set(d, prefix) for d in data]
 
     def _filename(self, id, prefix):
-        path = os.path.normpath(config.get('database', 'path'))
-        filename = os.path.join(path, prefix, id[0:2], id[2:4], id)
+        filename = os.path.join(PATH, prefix, id[0:2], id[2:4], id)
         filename = os.path.normpath(filename)
-        if not filename.startswith(path):
+        if not filename.startswith(PATH):
             raise ValueError('Bad prefix')
         return filename
 
diff --git a/trytond/trytond/tests/test_field_binary.py b/trytond/trytond/tests/test_field_binary.py
index 45d47ad72f..872f45c2e3 100644
--- a/trytond/trytond/tests/test_field_binary.py
+++ b/trytond/trytond/tests/test_field_binary.py
@@ -6,7 +6,7 @@ import unittest
 
 from sql import Literal
 
-from trytond.config import config
+from trytond import filestore
 from trytond.model import fields
 from trytond.model.exceptions import (
     RequiredValidationError, SQLConstraintError)
@@ -25,10 +25,11 @@ class FieldBinaryTestCase(unittest.TestCase):
         activate_module('tests')
 
     def setUp(self):
-        path = config.get('database', 'path')
+        super().setUp()
+        path = filestore.PATH
         dtemp = tempfile.mkdtemp()
-        config.set('database', 'path', dtemp)
-        self.addCleanup(config.set, 'database', 'path', path)
+        filestore.PATH = dtemp
+        self.addCleanup(setattr, filestore, 'PATH', path)
         self.addCleanup(shutil.rmtree, dtemp)
 
     @with_transaction()