diff --git a/TODO.md b/TODO.md
deleted file mode 100644
index b358efbbc9..0000000000
--- a/TODO.md
+++ /dev/null
@@ -1,5 +0,0 @@
-- https://github.com/preactjs/preact/pull/4358
-- https://github.com/preactjs/preact/pull/4361
-- Remove deprecated lifecycle methods
-- Put createPortal into core
-- Implement hydration 2.0
diff --git a/src/diff/index.js b/src/diff/index.js
index e6b22b810d..f82dd392f0 100644
--- a/src/diff/index.js
+++ b/src/diff/index.js
@@ -248,7 +248,7 @@ export function diff(
 			c.state = c._nextState;
 
 			if (c.getChildContext != null) {
-				globalContext = assign({}, globalContext, c.getChildContext());
+				globalContext = assign(assign({}, globalContext), c.getChildContext());
 			}
 
 			if (isClassComponent && !isNew && c.getSnapshotBeforeUpdate != null) {
@@ -300,9 +300,8 @@ export function diff(
 					newVNode._dom = oldDom;
 				} else {
 					for (let i = excessDomChildren.length; i--; ) {
-						if (excessDomChildren[i]) {
-							excessDomChildren[i].remove();
-						}
+						const child = excessDomChildren[i];
+						if (child) child.remove();
 					}
 				}
 			} else {
@@ -544,7 +543,8 @@ function diffElementNodes(
 			// Remove children that are not part of any vnode.
 			if (excessDomChildren != null) {
 				for (i = excessDomChildren.length; i--; ) {
-					if (excessDomChildren[i]) excessDomChildren[i].remove();
+					const child = excessDomChildren[i];
+					if (child) child.remove();
 				}
 			}
 		}
@@ -643,7 +643,7 @@ export function unmount(vnode, parentVNode, skipRemove) {
 		}
 	}
 
-	if (!skipRemove && vnode._dom != null && typeof vnode.type != 'function') {
+	if (!skipRemove && vnode._dom != null && vnode._dom.parentNode) {
 		vnode._dom.remove();
 	}
 
diff --git a/src/index.d.ts b/src/index.d.ts
index 08bc00fd25..92b5d49d27 100644
--- a/src/index.d.ts
+++ b/src/index.d.ts
@@ -299,16 +299,6 @@ interface ContainerNode {
 }
 
 export function render(vnode: ComponentChild, parent: ContainerNode): void;
-/**
- * @deprecated Will be removed in v11.
- *
- * Replacement Preact 10+ implementation can be found here: https://gist.github.com/developit/f4c67a2ede71dc2fab7f357f39cff28c
- */
-export function render(
-	vnode: ComponentChild,
-	parent: ContainerNode,
-	replaceNode?: Element | Text
-): void;
 export function hydrate(vnode: ComponentChild, parent: ContainerNode): void;
 export function cloneElement(
 	vnode: VNode<any>,
diff --git a/src/render.js b/src/render.js
index 97206fc043..e87f81a988 100644
--- a/src/render.js
+++ b/src/render.js
@@ -1,4 +1,4 @@
-import { EMPTY_OBJ } from './constants';
+import { EMPTY_OBJ, MODE_HYDRATE } from './constants';
 import { commitRoot, diff } from './diff/index';
 import { createElement, Fragment } from './create-element';
 import options from './options';
@@ -8,10 +8,8 @@ import { slice } from './util';
  * Render a Preact virtual node into a DOM element
  * @param {import('./internal').ComponentChild} vnode The virtual node to render
  * @param {import('./internal').PreactElement} parentDom The DOM element to render into
- * @param {import('./internal').PreactElement | object} [replaceNode] Optional: Attempt to re-use an
- * existing DOM tree rooted at `replaceNode`
  */
-export function render(vnode, parentDom, replaceNode) {
+export function render(vnode, parentDom) {
 	// https://github.com/preactjs/preact/issues/3794
 	if (parentDom == document) {
 		parentDom = document.documentElement;
@@ -19,10 +17,8 @@ export function render(vnode, parentDom, replaceNode) {
 
 	if (options._root) options._root(vnode, parentDom);
 
-	// We abuse the `replaceNode` parameter in `hydrate()` to signal if we are in
-	// hydration mode or not by passing the `hydrate` function instead of a DOM
-	// element..
-	let isHydrating = replaceNode === hydrate;
+	// @ts-expect-error
+	let isHydrating = !!(vnode && vnode._flags & MODE_HYDRATE);
 
 	// To be able to support calling `render()` multiple times on the same
 	// DOM node, we need to obtain a reference to the previous tree. We do
@@ -65,5 +61,7 @@ export function render(vnode, parentDom, replaceNode) {
  * @param {import('./internal').PreactElement} parentDom The DOM element to update
  */
 export function hydrate(vnode, parentDom) {
-	render(vnode, parentDom, hydrate);
+	// @ts-expect-error
+	vnode._flags |= MODE_HYDRATE;
+	render(vnode, parentDom);
 }
diff --git a/src/util.js b/src/util.js
index 8b112f69a2..282ab898d0 100644
--- a/src/util.js
+++ b/src/util.js
@@ -1,5 +1,17 @@
 import { EMPTY_ARR } from './constants';
 
 export const isArray = Array.isArray;
-export const assign = Object.assign;
 export const slice = EMPTY_ARR.slice;
+
+/**
+ * Assign properties from `props` to `obj`
+ * @template O, P The obj and props types
+ * @param {O} obj The object to copy properties to
+ * @param {P} props The object to copy properties from
+ * @returns {O & P}
+ */
+export function assign(obj, props) {
+	// @ts-expect-error We change the type of `obj` to be `O & P`
+	for (let i in props) obj[i] = props[i];
+	return /** @type {O & P} */ (obj);
+}