diff --git a/addons/web/static/src/js/views/form_widgets.js b/addons/web/static/src/js/views/form_widgets.js
index 25b4fbed8ba..515ba674eb7 100644
--- a/addons/web/static/src/js/views/form_widgets.js
+++ b/addons/web/static/src/js/views/form_widgets.js
@@ -1144,7 +1144,7 @@ var FieldBinary = common.AbstractField.extend(common.ReinitializeFieldMixin, {
                     'id': this.view.datarecord.id,
                     'field': this.name,
                     'filename_field': filename_fieldname,
-                    'filename': filename_field ? filename_field.get('value') : null,
+                    'filename': filename_field ? filename_field.get('value') : "",
                     'download': true,
                     'data': utils.is_bin_size(value) ? null : value,
                 },
diff --git a/odoo/addons/base/ir/ir_http.py b/odoo/addons/base/ir/ir_http.py
index df15e45df22..c01e6d4a4ea 100644
--- a/odoo/addons/base/ir/ir_http.py
+++ b/odoo/addons/base/ir/ir_http.py
@@ -303,9 +303,9 @@ class IrHttp(models.AbstractModel):
         if not filename:
             if filename_field in obj:
                 filename = obj[filename_field]
-            elif module_resource_path:
+            if not filename and module_resource_path:
                 filename = os.path.basename(module_resource_path)
-            else:
+            if not filename:
                 filename = "%s-%s-%s" % (obj._name, obj.id, field)
 
         # mimetype
@@ -320,6 +320,11 @@ class IrHttp(models.AbstractModel):
             if not mimetype:
                 mimetype = guess_mimetype(base64.b64decode(content), default=default_mimetype)
 
+        # extension
+        extension = mimetypes.guess_extension(mimetype)
+        if extension and not filename.endswith(extension):
+            filename = "%s%s" % (filename, extension)
+
         headers += [('Content-Type', mimetype), ('X-Content-Type-Options', 'nosniff')]
 
         # cache