diff --git a/README.md b/README.md
index 03ebcb6..7fdfe83 100644
--- a/README.md
+++ b/README.md
@@ -577,6 +577,8 @@ Every single built-in component's props can be dynamically extended using any on
 />
 ```
 
+If used, **a callback prop must return an valid object**, even if it's an empty one.
+
 These callbacks are executed with each render of the element with four parameters:
  1. Table State
  2. RowInfo (undefined if not applicable)