diff --git a/doc/en/scripting/builtins/libapp.md b/doc/en/scripting/builtins/libapp.md
index 06365fc99..f3d46238f 100644
--- a/doc/en/scripting/builtins/libapp.md
+++ b/doc/en/scripting/builtins/libapp.md
@@ -172,7 +172,9 @@ app.start_background_instance(
     -- script file
     app_script: string,
     -- log file
-    output_file: string | nil
+    output_file: string,
+    -- project parameters (can be read with vc.get_project_arg(name))
+    project_args: table<string, string> | nil
 ) -> int
 
 -- Checks if the engine sub-instance is alive.
diff --git a/doc/ru/scripting/builtins/libapp.md b/doc/ru/scripting/builtins/libapp.md
index 53a2224f2..71886a61f 100644
--- a/doc/ru/scripting/builtins/libapp.md
+++ b/doc/ru/scripting/builtins/libapp.md
@@ -162,7 +162,9 @@ app.start_background_instance(
     -- файл сценария
     app_script: string,
     -- файл лога
-    output_file: string | nil
+    output_file: string,
+    -- параметры проекта, что будут доступны через vc.get_project_arg(name)
+    project_args: table<string, string> | nil,
 ) -> int
 
 -- Проверяет, жив ли под-экземпляр движка.