diff --git a/packages/happy-dom/src/query-selector/SelectorParser.ts b/packages/happy-dom/src/query-selector/SelectorParser.ts
index da6875b0..eb960dcd 100644
--- a/packages/happy-dom/src/query-selector/SelectorParser.ts
+++ b/packages/happy-dom/src/query-selector/SelectorParser.ts
@@ -25,7 +25,7 @@ import ISelectorPseudo from './ISelectorPseudo.js';
  * Group 17: Combinator.
  */
 const SELECTOR_REGEXP =
-	/(\*)|([a-zA-Z0-9-]+)|#((?:[a-zA-Z0-9-_]|\\.)+)|\.((?:[a-zA-Z0-9-_]|\\.)+)|\[([a-zA-Z0-9-_]+)\]|\[([a-zA-Z0-9-_]+)\s*([~|^$*]{0,1})\s*=\s*["']{1}([^"']*)["']{1}\s*(s|i){0,1}\]|\[([a-zA-Z0-9-_]+)\s*([~|^$*]{0,1})\s*=\s*([^\]]*)\]|:([a-zA-Z-]+)\s*\(([^)]+\)?)\)|:([a-zA-Z-]+)|::([a-zA-Z-]+)|([\s,+>]*)/gm;
+	/(\*)|([a-zA-Z0-9-]+)|#((?:[a-zA-Z0-9-_]|\\.)+)|\.((?:[a-zA-Z0-9-_]|\\.)+)|\[([a-zA-Z0-9-_\\:]+)\]|\[([a-zA-Z0-9-_\\:]+)\s*([~|^$*]{0,1})\s*=\s*["']{1}([^"']*)["']{1}\s*(s|i){0,1}\]|\[([a-zA-Z0-9-_]+)\s*([~|^$*]{0,1})\s*=\s*([^\]]*)\]|:([a-zA-Z-]+)\s*\(([^)]+)\){0,1}|:([a-zA-Z-]+)|::([a-zA-Z-]+)|([\s,+>]*)/gm;
 
 /**
  * Escaped Character RegExp.
diff --git a/packages/happy-dom/src/xml-parser/XMLParser.ts b/packages/happy-dom/src/xml-parser/XMLParser.ts
index b5452b57..079965c0 100755
--- a/packages/happy-dom/src/xml-parser/XMLParser.ts
+++ b/packages/happy-dom/src/xml-parser/XMLParser.ts
@@ -42,7 +42,7 @@ const MARKUP_REGEXP =
  * Group 9: Attribute name when the attribute has no value (e.g. "disabled" in "<div disabled>").
  */
 const ATTRIBUTE_REGEXP =
-	/\s*([a-zA-Z0-9-_:.$@?]+) *= *([a-zA-Z0-9-_:.$@?{}/]+)|\s*([a-zA-Z0-9-_:.$@?]+) *= *"([^"]*)("{0,1})|\s*([a-zA-Z0-9-_:.$@?]+) *= *'([^']*)('{0,1})|\s*([a-zA-Z0-9-_:.$@?]+)/gm;
+	/\s*([a-zA-Z0-9-_:.$@?\\]+) *= *([a-zA-Z0-9-_:.$@?{}/]+)|\s*([a-zA-Z0-9-_:.$@?\\]+) *= *"([^"]*)("{0,1})|\s*([a-zA-Z0-9-_:.$@?\\]+) *= *'([^']*)('{0,1})|\s*([a-zA-Z0-9-_:.$@?\\]+)/gm;
 
 enum MarkupReadStateEnum {
 	startOrEndTag = 'startOrEndTag',
diff --git a/packages/happy-dom/test/query-selector/QuerySelector.test.ts b/packages/happy-dom/test/query-selector/QuerySelector.test.ts
index 0a89cce2..2a561b40 100644
--- a/packages/happy-dom/test/query-selector/QuerySelector.test.ts
+++ b/packages/happy-dom/test/query-selector/QuerySelector.test.ts
@@ -847,6 +847,31 @@ describe('QuerySelector', () => {
 			expect(elements3[1] === container.children[0].children[1].children[2]).toBe(true);
 		});
 
+		it('Returns all elements matching the selector without ending parenthese "button:not([type]"', () => {
+			const container = document.createElement('div');
+			container.innerHTML = `
+				<button></button>
+                <button type="submit"></button>
+                <button></button>
+			`;
+			const elements = container.querySelectorAll('button:not([type]');
+			expect(elements.length).toBe(2);
+			expect(elements[0]).toBe(container.children[0]);
+			expect(elements[1]).toBe(container.children[2]);
+		});
+
+		it('Returns all elements matching the invalid selector "[q\\:shadowroot]"', () => {
+			const container = document.createElement('div');
+			container.innerHTML = `
+				<span q\\:shadowroot></span>
+                <button></button>
+                <article></article>
+			`;
+			const elements = container.querySelectorAll('[q\\:shadowroot]');
+			expect(elements.length).toBe(1);
+			expect(elements[0]).toBe(container.children[0]);
+		});
+
 		it('Returns all elements matching "input:not([type]):not([list])" to verify that "screen.getByRole(\'checkbox\')" works in Testing Library.', () => {
 			const container = document.createElement('div');