diff --git a/odoo/addons/base/ir/ir_qweb/assetsbundle.py b/odoo/addons/base/ir/ir_qweb/assetsbundle.py
index f2221e9f7cd..e3c0b66f8cc 100644
--- a/odoo/addons/base/ir/ir_qweb/assetsbundle.py
+++ b/odoo/addons/base/ir/ir_qweb/assetsbundle.py
@@ -388,7 +388,7 @@ class AssetsBundle(object):
             if '.' not in ref and line not in imports and not ref.startswith(('.', '/', '~')):
                 imports.append(line)
                 return line
-            msg = "Local import '%s' is forbidden for security reasons." % ref
+            msg = "Local import '%s' is forbidden for security reasons. Please remove all @import \"your_file.less\" imports in your custom less files. In Odoo you have to import all less files in the assets, and not through the @import statement." % ref
             _logger.warning(msg)
             self.css_errors.append(msg)
             return ''