diff --git a/packages/happy-dom/src/event/events/IKeyboardEventInit.ts b/packages/happy-dom/src/event/events/IKeyboardEventInit.ts
index d04f02a65..6144e71e6 100644
--- a/packages/happy-dom/src/event/events/IKeyboardEventInit.ts
+++ b/packages/happy-dom/src/event/events/IKeyboardEventInit.ts
@@ -10,4 +10,9 @@ export default interface IKeyboardEventInit extends IUIEventInit {
 	metaKey?: boolean;
 	repeat?: boolean;
 	isComposing?: boolean;
+
+	/**
+	 * @deprecated
+	 */
+	keyCode?: number;
 }
diff --git a/packages/happy-dom/src/event/events/KeyboardEvent.ts b/packages/happy-dom/src/event/events/KeyboardEvent.ts
index 632c60f1a..86327e25a 100644
--- a/packages/happy-dom/src/event/events/KeyboardEvent.ts
+++ b/packages/happy-dom/src/event/events/KeyboardEvent.ts
@@ -19,6 +19,11 @@ export default class KeyboardEvent extends UIEvent {
 	public readonly repeat: boolean;
 	public readonly shiftKey: boolean;
 
+	/**
+	 * @deprecated
+	 */
+	public readonly keyCode: number;
+
 	/**
 	 * Constructor.
 	 *
@@ -37,5 +42,6 @@ export default class KeyboardEvent extends UIEvent {
 		this.metaKey = eventInit?.metaKey ?? false;
 		this.repeat = eventInit?.repeat ?? false;
 		this.shiftKey = eventInit?.shiftKey ?? false;
+		this.keyCode = eventInit?.keyCode ?? 0;
 	}
 }