diff --git a/docs/_docs/running-advanced-configuration.md b/docs/_docs/running-advanced-configuration.md
index 5512f60cb..7db27fb1c 100644
--- a/docs/_docs/running-advanced-configuration.md
+++ b/docs/_docs/running-advanced-configuration.md
@@ -24,6 +24,10 @@ otherwise the application will fail to start.
 Configure the duration for which comment counts are cached for, parsed by
 [ms](https://www.npmjs.com/package/ms){:target="_blank"}. (Default `1hr`)
 
+## TALK_DEFAULT_LANG
+
+Specify the default translation language. (Default `en`)
+
 ## TALK_DEFAULT_STREAM_TAB
 
 Specify the default stream tab in the admin. (Default `all`)
@@ -439,4 +443,4 @@ Could be read as:
   again, then they must have two of their comments approved in order to get
   added back to the queue.
 - At the moment of writing, behavior is not attached to the flagging
-  reliability, but it is recorded.
\ No newline at end of file
+  reliability, but it is recorded.