diff --git a/odoo/addons/test_new_api/models/test_new_api.py b/odoo/addons/test_new_api/models/test_new_api.py
index 45398e74df6..a574b5b8514 100644
--- a/odoo/addons/test_new_api/models/test_new_api.py
+++ b/odoo/addons/test_new_api/models/test_new_api.py
@@ -941,7 +941,10 @@ class BinarySvg(models.Model):
     name = fields.Char(required=True)
     image_attachment = fields.Binary(attachment=True)
     image_wo_attachment = fields.Binary(attachment=False)
-
+    image_wo_attachment_related = fields.Binary(
+        "image wo attachment", related="image_wo_attachment",
+        store=True, attachment=False,
+    )
 
 class MonetaryBase(models.Model):
     _name = 'test_new_api.monetary_base'
diff --git a/odoo/addons/test_new_api/tests/test_web_save.py b/odoo/addons/test_new_api/tests/test_web_save.py
index 7d17e61848c..41678a61a40 100644
--- a/odoo/addons/test_new_api/tests/test_web_save.py
+++ b/odoo/addons/test_new_api/tests/test_web_save.py
@@ -1,6 +1,8 @@
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 from odoo.tests.common import TransactionCase
 
+from odoo.addons.base.tests.test_mimetypes import SVG, JPG
+
 
 class TestWebSave(TransactionCase):
 
@@ -36,3 +38,39 @@ class TestWebSave(TransactionCase):
         # Modify an existing record, with unity specification
         result = person.web_save({'name': 'lpe'}, {'display_name': {}})
         self.assertEqual(result, [{'id': person.id, 'display_name': 'lpe'}])
+
+    def test_web_save_computed_stored_binary(self):
+        [result] = self.env['test_new_api.binary_svg'].web_save(
+            {'name': 'test', 'image_wo_attachment': SVG},
+            {'image_wo_attachment': {}, 'image_wo_attachment_related': {}},
+        )
+        self.assertEqual(result['image_wo_attachment'], '400 bytes')  # From PostgreSQL
+        self.assertEqual(result['image_wo_attachment_related'], b'400.00 bytes')  # From human_size
+
+        # check cache values
+        record = self.env['test_new_api.binary_svg'].browse(result['id'])
+        self.assertEqual(record.image_wo_attachment, SVG)
+        self.assertEqual(record.image_wo_attachment, record.image_wo_attachment_related)
+
+        # check database values
+        self.env.invalidate_all()
+        self.assertEqual(record.image_wo_attachment, SVG)
+        self.assertEqual(record.image_wo_attachment, record.image_wo_attachment_related)
+
+        # check web_save() on existing record
+        self.env.invalidate_all()
+        [result] = record.web_save(
+            {'image_wo_attachment': JPG},
+            {'image_wo_attachment': {}, 'image_wo_attachment_related': {}},
+        )
+        self.assertEqual(result['image_wo_attachment'], '727 bytes')  # From PostgreSQL
+        self.assertEqual(result['image_wo_attachment_related'], b'727.00 bytes')  # From human_size
+
+        # check cache values
+        self.assertEqual(record.image_wo_attachment, JPG.encode())
+        self.assertEqual(record.image_wo_attachment, record.image_wo_attachment_related)
+
+        # check database values
+        self.env.invalidate_all()
+        self.assertEqual(record.image_wo_attachment, JPG.encode())
+        self.assertEqual(record.image_wo_attachment, record.image_wo_attachment_related)
diff --git a/odoo/fields.py b/odoo/fields.py
index 86af1dea939..5a1943064c6 100644
--- a/odoo/fields.py
+++ b/odoo/fields.py
@@ -2406,18 +2406,18 @@ class Binary(Field):
             for record_no_bin_size, record in zip(records_no_bin_size, records):
                 try:
                     value = cache.get(record_no_bin_size, self)
-                    try:
-                        value = base64.b64decode(value)
-                    except (TypeError, binascii.Error):
-                        pass
+                    # don't decode non-attachments to be consistent with pg_size_pretty
+                    if not (self.store and self.column_type):
+                        with contextlib.suppress(TypeError, binascii.Error):
+                            value = base64.b64decode(value)
                     try:
                         if isinstance(value, (bytes, _BINARY)):
                             value = human_size(len(value))
                     except (TypeError):
                         pass
                     cache_value = self.convert_to_cache(value, record)
-                    dirty = self.column_type and self.store and any(records._ids)
-                    cache.set(record, self, cache_value, dirty=dirty)
+                    # the dirty flag is independent from this assignment
+                    cache.set(record, self, cache_value, check_dirty=False)
                 except CacheMiss:
                     pass
         else: