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+---
+'astro': major
+---
+
+The `locals` object can no longer be overridden
+
+Middleware, API endpoints, and pages can no longer override the `locals` object in its entirety. You can still append values onto the object, but you can not replace the entire object and delete its existing values.
+
+If you were previously overwriting like so:
+
+```js
+ctx.locals = {
+  one: 1,
+  two: 2
+}
+```
+
+This can be changed to an assignment on the existing object instead:
+
+```js
+Object.assign(ctx.locals, {
+  one: 1,
+  two: 2
+})
+```