diff --git a/odoo/addons/base/models/ir_actions_report.py b/odoo/addons/base/models/ir_actions_report.py
index ec3803fd0f4..3d38c37b69d 100644
--- a/odoo/addons/base/models/ir_actions_report.py
+++ b/odoo/addons/base/models/ir_actions_report.py
@@ -395,7 +395,7 @@ class IrActionsReport(models.Model):
                 res_ids.append(None)
 
         if not bodies:
-            body = b''.join(lxml.html.tostring(c, encoding='utf-8') for c in body_parent.getchildren())
+            body = ''.join(lxml.html.tostring(c, encoding='unicode') for c in body_parent.getchildren())
             bodies.append(body)
 
         # Get paperformat arguments set in the root html tag. They are prioritized over
@@ -452,13 +452,13 @@ class IrActionsReport(models.Model):
         if header:
             head_file_fd, head_file_path = tempfile.mkstemp(suffix='.html', prefix='report.header.tmp.')
             with closing(os.fdopen(head_file_fd, 'wb')) as head_file:
-                head_file.write(header)
+                head_file.write(header.encode())
             temporary_files.append(head_file_path)
             files_command_args.extend(['--header-html', head_file_path])
         if footer:
             foot_file_fd, foot_file_path = tempfile.mkstemp(suffix='.html', prefix='report.footer.tmp.')
             with closing(os.fdopen(foot_file_fd, 'wb')) as foot_file:
-                foot_file.write(footer)
+                foot_file.write(footer.encode())
             temporary_files.append(foot_file_path)
             files_command_args.extend(['--footer-html', foot_file_path])
 
@@ -467,7 +467,7 @@ class IrActionsReport(models.Model):
             prefix = '%s%d.' % ('report.body.tmp.', i)
             body_file_fd, body_file_path = tempfile.mkstemp(suffix='.html', prefix=prefix)
             with closing(os.fdopen(body_file_fd, 'wb')) as body_file:
-                body_file.write(body)
+                body_file.write(body.encode())
             paths.append(body_file_path)
             temporary_files.append(body_file_path)