diff --git a/__tests__/paths.spec.ts b/__tests__/paths.spec.ts
index e93cc78..2941781 100644
--- a/__tests__/paths.spec.ts
+++ b/__tests__/paths.spec.ts
@@ -42,6 +42,20 @@ describe('Path generation', () => {
 		beforeEach(() => {
 			window._oc_webroot = ''
 			window._oc_appswebroots = { forms: '/apps-extra/forms' }
+
+			window.OC = {
+				coreApps: ['', 'admin', 'log', 'core/search', 'core', '3rdparty'],
+			}
+		})
+
+		test('missing core apps global variable', () => {
+			delete window.OC.coreApps
+			expect(generateFilePath('forms', '', 'file.js')).toBe('/apps-extra/forms/file.js')
+		})
+
+		test('missing OC global variable (unit tests)', () => {
+			delete window.OC
+			expect(generateFilePath('forms', '', 'file.js')).toBe('/apps-extra/forms/file.js')
 		})
 
 		test('non core PHP index file', () => {
diff --git a/lib/index.ts b/lib/index.ts
index 969fd21..1c08b76 100644
--- a/lib/index.ts
+++ b/lib/index.ts
@@ -162,9 +162,10 @@ export const imagePath = (app: string, file: string) => {
  * @return {string} URL with webroot for a file in an app
  */
 export const generateFilePath = (app: string, type: string, file: string) => {
-	const isCore = window?.OC?.coreApps?.indexOf(app) !== -1
+	const isCore = window?.OC?.coreApps?.includes(app) ?? false
+	const isPHP = file.slice(-3) === 'php'
 	let link = getRootUrl()
-	if (file.substring(file.length - 3) === 'php' && !isCore) {
+	if (isPHP && !isCore) {
 		link += `/index.php/apps/${app}`
 		if (type) {
 			link += `/${encodeURI(type)}`
@@ -172,32 +173,26 @@ export const generateFilePath = (app: string, type: string, file: string) => {
 		if (file !== 'index.php') {
 			link += `/${file}`
 		}
-	} else if (file.substring(file.length - 3) !== 'php' && !isCore) {
+	} else if (!isPHP && !isCore) {
 		link = getAppRootUrl(app)
 		if (type) {
-			link += '/' + type + '/'
+			link += `/${type}/`
 		}
-		if (link.substring(link.length - 1) !== '/') {
+		if (link.at(-1) !== '/') {
 			link += '/'
 		}
 		link += file
 	} else {
 		if ((app === 'settings' || app === 'core' || app === 'search') && type === 'ajax') {
-			link += '/index.php/'
-		} else {
-			link += '/'
+			link += '/index.php'
 		}
-		if (!isCore) {
-			link += 'apps/'
-		}
-		if (app !== '') {
-			app += '/'
-			link += app
+		if (app) {
+			link += `/${app}`
 		}
 		if (type) {
-			link += type + '/'
+			link += `/${type}`
 		}
-		link += file
+		link += `/${file}`
 	}
 	return link
 }