diff --git a/addons/web/controllers/main.py b/addons/web/controllers/main.py
index 1907064bd6b..061c1c57926 100644
--- a/addons/web/controllers/main.py
+++ b/addons/web/controllers/main.py
@@ -1544,7 +1544,7 @@ class Binary(http.Controller):
         try:
             data = ufile.read()
             args = [len(data), ufile.filename,
-                    ufile.content_type, base64.b64encode(data)]
+                    ufile.content_type, pycompat.to_text(base64.b64encode(data))]
         except Exception as e:
             args = [False, str(e)]
         return out % (json.dumps(callback), json.dumps(args)) if callback else json.dumps(args)