diff --git a/packages/happy-dom/src/nodes/document/Document.ts b/packages/happy-dom/src/nodes/document/Document.ts
index 1e1493a2d..7190461c4 100644
--- a/packages/happy-dom/src/nodes/document/Document.ts
+++ b/packages/happy-dom/src/nodes/document/Document.ts
@@ -345,6 +345,10 @@ export default class Document extends Node implements IDocument {
 	 * @returns Active element.
 	 */
 	public get activeElement(): IHTMLElement {
+		if (this._activeElement && !this._activeElement.isConnected) {
+			this._activeElement = null;
+		}
+
 		if (this._activeElement) {
 			let rootNode: IShadowRoot | IDocument = <IShadowRoot | IDocument>(
 				this._activeElement.getRootNode()
diff --git a/packages/happy-dom/src/nodes/node/Node.ts b/packages/happy-dom/src/nodes/node/Node.ts
index 5abb8e419..ab40eec9b 100644
--- a/packages/happy-dom/src/nodes/node/Node.ts
+++ b/packages/happy-dom/src/nodes/node/Node.ts
@@ -552,6 +552,9 @@ export default class Node extends EventTarget implements INode {
 			if (isConnected && this.connectedCallback) {
 				this.connectedCallback();
 			} else if (!isConnected && this.disconnectedCallback) {
+				if (this.ownerDocument['_activeElement'] === this) {
+					this.ownerDocument['_activeElement'] = null;
+				}
 				this.disconnectedCallback();
 			}
 
diff --git a/packages/happy-dom/src/nodes/shadow-root/ShadowRoot.ts b/packages/happy-dom/src/nodes/shadow-root/ShadowRoot.ts
index 59c937848..8fba913b0 100644
--- a/packages/happy-dom/src/nodes/shadow-root/ShadowRoot.ts
+++ b/packages/happy-dom/src/nodes/shadow-root/ShadowRoot.ts
@@ -54,7 +54,7 @@ export default class ShadowRoot extends DocumentFragment implements IShadowRoot
 	 */
 	public get activeElement(): IHTMLElement {
 		const activeElement: IHTMLElement = this.ownerDocument['_activeElement'];
-		if (activeElement && activeElement.getRootNode() === this) {
+		if (activeElement && activeElement.isConnected && activeElement.getRootNode() === this) {
 			return activeElement;
 		}
 		return null;
diff --git a/packages/happy-dom/test/nodes/document/Document.test.ts b/packages/happy-dom/test/nodes/document/Document.test.ts
index 86f3b1b6c..f93374aed 100644
--- a/packages/happy-dom/test/nodes/document/Document.test.ts
+++ b/packages/happy-dom/test/nodes/document/Document.test.ts
@@ -320,6 +320,22 @@ describe('Document', () => {
 			expect(document.activeElement === document.body).toBe(true);
 		});
 
+		it('Unsets the active element when it gets disconnected.', () => {
+			const div = <IHTMLElement>document.createElement('div');
+
+			document.appendChild(div);
+
+			expect(document.activeElement === document.body).toBe(true);
+
+			div.focus();
+
+			expect(document.activeElement === div).toBe(true);
+
+			div.remove();
+
+			expect(document.activeElement === document.body).toBe(true);
+		});
+
 		it('Returns the first custom element that has document as root node when the focused element is nestled in multiple shadow roots.', () => {
 			class CustomElementA extends (<Window>window).HTMLElement {
 				constructor() {
diff --git a/packages/happy-dom/test/nodes/shadow-root/ShadowRoot.test.ts b/packages/happy-dom/test/nodes/shadow-root/ShadowRoot.test.ts
index 7b9045c3a..3578e1135 100644
--- a/packages/happy-dom/test/nodes/shadow-root/ShadowRoot.test.ts
+++ b/packages/happy-dom/test/nodes/shadow-root/ShadowRoot.test.ts
@@ -68,6 +68,26 @@ describe('ShadowRoot', () => {
 
 			expect(shadowRoot.activeElement === null).toBe(true);
 		});
+
+		it('Unsets the active element when it gets disconnected.', () => {
+			const customElement = document.createElement('custom-element');
+			const shadowRoot = customElement.shadowRoot;
+			const div = <IHTMLElement>document.createElement('div');
+
+			document.body.appendChild(customElement);
+
+			shadowRoot.appendChild(div);
+
+			expect(shadowRoot.activeElement === null).toBe(true);
+
+			div.focus();
+
+			expect(shadowRoot.activeElement === div).toBe(true);
+
+			customElement.remove();
+
+			expect(shadowRoot.activeElement === null).toBe(true);
+		});
 	});
 
 	describe('toString()', () => {