diff --git a/_includes/lang.html b/_includes/lang.html
index ab5b819..fb0bdc4 100644
--- a/_includes/lang.html
+++ b/_includes/lang.html
@@ -1,9 +1,10 @@
{% comment %}
Detect appearance language and return it through variable "lang"
{% endcomment %}
-
-{% if page.lang %}
+{% if site.data.locales[page.lang] %}
{% assign lang = page.lang %}
+{% else if site.data.locales[site.lang] %}
+ {% assign lang = site.lang %}
{% else %}
{% assign lang = 'en' %}
{% endif %}
diff --git a/_layouts/default.html b/_layouts/default.html
index 71f9fd1..8194764 100644
--- a/_layouts/default.html
+++ b/_layouts/default.html
@@ -12,7 +12,6 @@
{% capture prefer_mode %}data-mode="{{ site.theme_mode }}"{% endcapture %}
{% endif %}
-
{% include head.html %}
@@ -76,10 +75,10 @@
- {% include js-selector.html %}
+ {% include js-selector.html lang=lang %}
{% if page.mermaid %}
- {% include mermaid.html %}
+ {% include mermaid.html lang=lang %}
{% endif %}
{% include_cached search-loader.html lang=lang %}