diff --git a/odoo/addons/test_new_api/models.py b/odoo/addons/test_new_api/models.py
index 6d90119aba7..3f45466efa3 100644
--- a/odoo/addons/test_new_api/models.py
+++ b/odoo/addons/test_new_api/models.py
@@ -525,6 +525,13 @@ class ModelBinary(models.Model):
     binary = fields.Binary()
     binary_related_store = fields.Binary("Binary Related Store", related='binary', store=True, readonly=False)
     binary_related_no_store = fields.Binary("Binary Related No Store", related='binary', store=False, readonly=False)
+    binary_computed = fields.Binary(compute='_compute_binary')
+
+    @api.depends('binary')
+    def _compute_binary(self):
+        # arbitrary value: 'bin_size' must have no effect
+        for record in self:
+            record.binary_computed = [(record.id, bool(record.binary))]
 
 
 class ModelImage(models.Model):
diff --git a/odoo/addons/test_new_api/tests/test_new_fields.py b/odoo/addons/test_new_api/tests/test_new_fields.py
index 692245c849c..da078a00137 100644
--- a/odoo/addons/test_new_api/tests/test_new_fields.py
+++ b/odoo/addons/test_new_api/tests/test_new_fields.py
@@ -1598,6 +1598,18 @@ class TestFields(common.TransactionCase):
         assertBinaryValue(record_no_bin_size, binary_value)
         assertBinaryValue(record_bin_size, binary_size)
 
+        # check computed binary field with arbitrary Python value
+        record = self.env['test_new_api.model_binary'].create({})
+        record.flush()
+        record.invalidate_cache()
+        record_no_bin_size = record.with_context(bin_size=False)
+        record_bin_size = record.with_context(bin_size=True)
+
+        expected_value = [(record.id, False)]
+        self.assertEqual(record.binary_computed, expected_value)
+        self.assertEqual(record_no_bin_size.binary_computed, expected_value)
+        self.assertEqual(record_bin_size.binary_computed, expected_value)
+
 
 class TestX2many(common.TransactionCase):
     def test_definition_many2many(self):
diff --git a/odoo/fields.py b/odoo/fields.py
index fdb56fc898a..f244eb56163 100644
--- a/odoo/fields.py
+++ b/odoo/fields.py
@@ -1921,7 +1921,8 @@ class Binary(Field):
                     except (TypeError, binascii.Error):
                         pass
                     try:
-                        value = human_size(len(value))
+                        if isinstance(value, (bytes, _BINARY)):
+                            value = human_size(len(value))
                     except (TypeError):
                         pass
                     cache_value = self.convert_to_cache(value, record)