diff --git a/packages/happy-dom/src/nodes/html-button-element/HTMLButtonElement.ts b/packages/happy-dom/src/nodes/html-button-element/HTMLButtonElement.ts
index ebf727de..74afecf7 100644
--- a/packages/happy-dom/src/nodes/html-button-element/HTMLButtonElement.ts
+++ b/packages/happy-dom/src/nodes/html-button-element/HTMLButtonElement.ts
@@ -1,7 +1,11 @@
 import HTMLElement from '../html-element/HTMLElement';
 import IHTMLButtonElement from './IHTMLButtonElement';
 
+const BUTTON_TYPES = ['submit', 'reset', 'button', 'menu'];
+
 /**
+
+We can improve performance a bit if we make the types as a constant.
  * HTML Button Element.
  *
  * Reference:
@@ -54,7 +58,7 @@ export default class HTMLButtonElement extends HTMLElement implements IHTMLButto
 	 * @returns Type
 	 */
 	public get type(): string {
-		return this.sanitizeType(this.getAttributeNS(null, 'type'));
+		return this._sanitizeType(this.getAttributeNS(null, 'type'));
 	}
 
 	/**
@@ -70,10 +74,10 @@ export default class HTMLButtonElement extends HTMLElement implements IHTMLButto
 	 *
 	 * @param type
 	 */
-	private sanitizeType(type: string): string {
+	protected _sanitizeType(type: string): string {
 		type = (type && type.toLowerCase()) || 'submit';
 
-		if (!['submit', 'reset', 'button', 'menu'].includes(type)) {
+		if (! BUTTON_TYPES.includes(type)) {
 			type = 'submit';
 		}