diff --git a/doc/hooks.md b/doc/hooks.md
index 3d609053..ed9797fc 100644
--- a/doc/hooks.md
+++ b/doc/hooks.md
@@ -181,6 +181,9 @@ class Counter extends owl.Component {
 }
 ```
 
+It is important to remember that `useState` only works with objects or arrays. It
+is necessary, since Owl needs to react to a change in state.
+
 ### `onMounted`
 
 `onMounted` is not a user hook, but is a building block designed to help make useful
diff --git a/doc/store.md b/doc/store.md
index 02549c9f..bb562edc 100644
--- a/doc/store.md
+++ b/doc/store.md
@@ -262,6 +262,10 @@ will only be rerendered whenever this part of the state changes. Otherwise, it
 will perform a strict equality check and will update the component every time this
 check fails.
 
+Also, it may not be obvious, but it is crucial to remember that the selector
+function should return an object or an array.  The reason is that it needs to be
+observed, otherwise the component would not be able to react to changes.
+
 ### `useDispatch`
 
 The `useDispatch` hook is useful when a component needs to be able to dispatch