diff --git a/src/nodes/html.ts b/src/nodes/html.ts
index b24cbe8..5708e33 100644
--- a/src/nodes/html.ts
+++ b/src/nodes/html.ts
@@ -158,7 +158,7 @@ export default class HTMLElement extends Node {
 			return 'null';
 		}
 
-		return JSON.stringify(attr.replace(/"/g, '"'));
+		return JSON.stringify(attr.replace(/"/g, '"')).replace(/\\t/g, '\t').replace(/\\n/g, '\n').replace(/\\r/g, '\r');
 	}
 
 	/**
diff --git a/test/tests/issues/240.js b/test/tests/issues/240.js
new file mode 100644
index 0000000..ea9046c
--- /dev/null
+++ b/test/tests/issues/240.js
@@ -0,0 +1,13 @@
+const { parse } = require('@test/test-target');
+
+describe('issue 240', function () {
+	it(`attribute should not changed`, function () {
+		const html = "<div unchanged='[\npreserve newline\n]'></div>";
+		const root = parse(html);
+		const div = root.firstChild
+		div.toString().should.eql(html);
+
+		div.setAttribute("append", "newAttribute");
+		div.toString().should.eql('<div unchanged="[\npreserve newline\n]" append="newAttribute"></div>');
+	});
+});