diff --git a/lib/default-theme/Navbar.vue b/lib/default-theme/Navbar.vue
index 6ad9bb20..12795665 100644
--- a/lib/default-theme/Navbar.vue
+++ b/lib/default-theme/Navbar.vue
@@ -58,7 +58,8 @@ export default {
       if (document.documentElement.clientWidth < MOBILE_DESKTOP_BREAKPOINT) {
         this.linksWrapMaxWidth = null
       } else {
-        this.linksWrapMaxWidth = this.$el.offsetWidth - NAVBAR_VERTICAL_PADDING - this.$refs.siteName.offsetWidth
+        this.linksWrapMaxWidth = this.$el.offsetWidth - NAVBAR_VERTICAL_PADDING -
+          (this.$refs.siteName && this.$refs.siteName.offsetWidth || 0)
       }
     }
     handleLinksWrapWidth()