diff --git a/doc/preview.txt b/doc/preview.txt
index 383a8f5..b4b74f5 100644
--- a/doc/preview.txt
+++ b/doc/preview.txt
@@ -68,6 +68,10 @@ Provider fields: ~
                                         receives a |preview.Context| and
                                         returns a string[].
 
+  {extra_args}       (string[]|function) Appended to {args} after evaluation.
+                                        Useful for adding flags to a preset
+                                        without replacing its defaults.
+
   {cwd}              (string|function)  Working directory. If a function,
                                         receives a |preview.Context|.
                                         Default: git root or file directory.