diff --git a/swh/core/logger.py b/swh/core/logger.py
--- a/swh/core/logger.py
+++ b/swh/core/logger.py
@@ -14,7 +14,7 @@
     current_task = None
 
 from psycopg2.extras import Json
-
+from swh.core import serializers
 
 EXTRA_LOGDATA_PREFIX = 'swh_'
 
@@ -27,6 +27,11 @@
     return logging.getLevelName(lvl).lower()
 
 
+class SWHJson(Json):
+    def dumps(self, obj):
+        return serializers.SWHJSONEncoder().encode(obj)
+
+
 class PostgresHandler(logging.Handler):
     """log handler that store messages in a Postgres DB
 
@@ -90,7 +95,7 @@
             }
 
         log_entry = (db_level_of_py_level(log_data['levelno']), msg,
-                     Json(extra_data), log_data['name'], self.fqdn,
+                     SWHJson(extra_data), log_data['name'], self.fqdn,
                      os.getpid())
         db = self._connect()
         with db.cursor() as cur:
diff --git a/swh/core/tests/test_logger.py b/swh/core/tests/test_logger.py
--- a/swh/core/tests/test_logger.py
+++ b/swh/core/tests/test_logger.py
@@ -3,6 +3,7 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+import base64
 import logging
 import os
 import unittest
@@ -39,6 +40,10 @@
         self.logger.info('notice',
                          extra={'swh_type': 'test entry', 'swh_data': 42})
         self.logger.warn('warning')
+        # Deal with bytes
+        data_as_bytes = b'some-data'
+        self.logger.error('error', extra={'swh_type': 'bytes test entry',
+                                          'swh_data': data_as_bytes})
 
         with self.conn.cursor() as cur:
             cur.execute('SELECT level, message, data, src_module FROM log')
@@ -48,3 +53,14 @@
                        self.modname),
                       db_log_entries)
         self.assertIn(('warning', 'warning', {}, self.modname), db_log_entries)
+
+        expected_data = base64.b85encode(data_as_bytes).decode('ascii')
+        self.assertIn(
+            ('error', 'error', {
+                'type': 'bytes test entry',
+                'data': {
+                    'd': expected_data,
+                    'swhtype': 'bytes',
+                }
+            }, self.modname),
+            db_log_entries)