diff --git a/README.md b/README.md
index 6623604..2e9f6c4 100644
--- a/README.md
+++ b/README.md
@@ -137,6 +137,14 @@ $(() => {
 });
 ```
 
+> **Special behaviour for dropzones:**
+>
+> `onComplete` only fires when `showFinishButton = true` (i.e. when the user clicks "Finish").
+>
+> `onUpdate` must be used when `showFinishButton = false`.
+>
+> Default value: `showFinishButton = false`
+
 ## Result
 
 The callbacks receive a `Array<UploadWidgetResult>`: