diff --git a/CHANGELOG b/CHANGELOG
index 8108c49fe9..c5b6eebeb1 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,4 @@
+* Unify PYSON string format
 * Forbid all white spaces except space in Char field
 
 Version 5.8.0 - 2020-11-02
diff --git a/trytond/pyson.py b/trytond/pyson.py
index 23b09cc04c..d79fefb876 100644
--- a/trytond/pyson.py
+++ b/trytond/pyson.py
@@ -769,4 +769,6 @@ CONTEXT = {
     'TimeDelta': TimeDelta,
     'Len': Len,
     'Id': Id,
+    'true': True,
+    'false': False,
 }
diff --git a/trytond/tests/test_pyson.py b/trytond/tests/test_pyson.py
index 66aae94eb5..bc8102312f 100644
--- a/trytond/tests/test_pyson.py
+++ b/trytond/tests/test_pyson.py
@@ -838,6 +838,14 @@ class PYSONTestCase(unittest.TestCase):
                 ]:
             self.assertEqual(pyson.PYSONDecoder(ctx).decode(eval), result)
 
+    def test_eval_true(self):
+        "Test PYSON.eval JS true"
+        self.assertEqual(eval('true', pyson.CONTEXT), True)
+
+    def test_eval_false(self):
+        "Test PYSON.eval JS false"
+        self.assertEqual(eval('false', pyson.CONTEXT), False)
+
 
 def suite():
     return unittest.TestLoader().loadTestsFromTestCase(PYSONTestCase)