diff --git a/layout/includes/third-party/newest-comments/artalk.pug b/layout/includes/third-party/newest-comments/artalk.pug
index 61e9c56..08143d9 100644
--- a/layout/includes/third-party/newest-comments/artalk.pug
+++ b/layout/includes/third-party/newest-comments/artalk.pug
@@ -1,6 +1,6 @@
 - const { server, site, option } = theme.artalk
-- const avatarCdn = option !== null && option.gravatar && option.gravatar.mirror
-- const avatarDefault = option !== null && option.gravatar && (option.gravatar.params || option.gravatar.default)
+- const avatarCdn = (option !== null && option.gravatar && option.gravatar.mirror) || ''
+- const avatarDefault = (option !== null && option.gravatar && (option.gravatar.params || option.gravatar.default)) || ''
 
 script.
   window.addEventListener('load', () => {