diff --git a/lib/RequestShortener.js b/lib/RequestShortener.js
index fd67f9814..3d9af0002 100644
--- a/lib/RequestShortener.js
+++ b/lib/RequestShortener.js
@@ -67,7 +67,7 @@ class RequestShortener {
 			result = result.replace(this.currentDirectoryRegExp, "!.");
 		}
 		if (this.parentDirectoryRegExp) {
-			result = result.replace(this.parentDirectoryRegExp, `!../`);
+			result = result.replace(this.parentDirectoryRegExp, "!../");
 		}
 		if (!this.buildinsAsModule && this.buildinsRegExp) {
 			result = result.replace(this.buildinsRegExp, "!(webpack)");
diff --git a/test/RequestShortener.unittest.js b/test/RequestShortener.unittest.js
new file mode 100644
index 000000000..f38c36fb8
--- /dev/null
+++ b/test/RequestShortener.unittest.js
@@ -0,0 +1,22 @@
+"use strict";
+
+const RequestShortener = require("../lib/RequestShortener");
+
+describe("RequestShortener", () => {
+	it("should create RequestShortener and shorten with ./ file in directory", () => {
+		const shortener = new RequestShortener("/foo/bar");
+		expect(shortener.shorten("/foo/bar/some.js")).toEqual("./some.js");
+	});
+
+	it("should create RequestShortener and shorten with ../ file in parent directory", () => {
+		const shortener = new RequestShortener("/foo/bar");
+		expect(shortener.shorten("/foo/baz/some.js")).toEqual("../baz/some.js");
+	});
+
+	it("should create RequestShortener and not shorten parent directory neighbor", () => {
+		const shortener = new RequestShortener("/foo/bar");
+		expect(shortener.shorten("/foo_baz/bar/some.js")).toEqual(
+			"/foo_baz/bar/some.js"
+		);
+	});
+});