diff --git a/CONFIGURATION.md b/CONFIGURATION.md
index 83b12f57..25c4e48d 100644
--- a/CONFIGURATION.md
+++ b/CONFIGURATION.md
@@ -113,6 +113,7 @@ modules:
   basic_auth:
     [ username: <string> ]
     [ password: <secret> ]
+    [ username_file: <filename> ]
     [ password_file: <filename> ]
 
   # Sets the `Authorization` header on every request with