diff --git a/index.js b/index.js
index d5991b6..e9eb01e 100644
--- a/index.js
+++ b/index.js
@@ -9,7 +9,7 @@ module.exports = function (options) {
 
 	options = options || {};
 	options.isLibrary = !!options.isLibrary;
-	options.fileName = options.fileName || (options.isLibrary ? 'library-preload.json' : 'Component-preload.js');
+	options.fileName = options.fileName || ((options.isLibrary ? 'library-preload.' : 'Component-preload.') + (options.format || 'js'));
 
 	if (typeof options.base !== 'string') {
 		throw new PluginError('gulp-ui5-preload', '`base` parameter required');
@@ -64,9 +64,11 @@ module.exports = function (options) {
 		var template = 'jQuery.sap.registerPreloadedModules(JSON_CONTENT);';
 		var suffix  = '.Component-preload';
 		if (options.isLibrary) {
-			template = 'JSON_CONTENT';
 			suffix  = '.library-preload';
 		}
+		if (options.fileName.slice(-4) === 'json') {
+			template = 'JSON_CONTENT';
+		}
 
 		var jsonContent = JSON.stringify(
 			{
diff --git a/readme.md b/readme.md
index 436eacb..b5f294b 100644
--- a/readme.md
+++ b/readme.md
@@ -71,7 +71,7 @@ The namespace at the `base` path. All source files are treated as sub-namespaces
 
 ##### fileName
 * Type: `string`
-* Default: 'Component-preload.js' or 'library-preload.json' (depends on `isLibrary` option)
+* Default: 'Component-preload.js' or 'library-preload.js' (depends on `isLibrary` option)
 
 File name of the combined file to emit.
 
@@ -79,7 +79,13 @@ File name of the combined file to emit.
 * Type: `boolean`
 * Default: false
 
-If set to `true` a `library-preload.json` file is emitted instead of a `Component-preload.js` file (default). The emitted file contents between those options vary a little bit.
+If set to `true` a `library-preload.js` file is emitted instead of a `Component-preload.js` file (default). The emitted file contents between those options vary a little bit.
+
+##### format
+* Type: `string`
+* Default: 'js'
+
+The output format. Can be set to 'json' in order to emit a `library-preload.json` file (which is required for UI5 versions < 1.40).
 
 ## License
 
diff --git a/test.js b/test.js
index c314776..b504713 100644
--- a/test.js
+++ b/test.js
@@ -30,8 +30,33 @@ lab.test('creates a preload file full of unicorns and zebras :-)', function (don
 	stream.end();
 });
 
-lab.test('creates a library-preload file full of unicorns and zebras :-)', function (done) {
+lab.test('creates a library-preload.js file full of unicorns and zebras :-)', function (done) {
 	var stream = ui5Preload({base: 'src/conf/ui', namespace: 'sap.pdms.fdn', isLibrary: true});
+	var expectedFile = 'jQuery.sap.registerPreloadedModules({\n\t"name": "sap.pdms.fdn.library-preload",\n\t"version": "2.0",\n\t"modules": {\n\t\t"sap/pdms/fdn/app/unicorns.js": "unicorns",\n\t\t\"sap/pdms/fdn/app/zebras.xml": "zebras"\n\t}\n});';
+
+	stream.write(new Vinyl({
+		base: __dirname,
+		path: __dirname + '/src/conf/ui/app/unicorns.js',
+		contents: new Buffer('unicorns')
+	}));
+
+	stream.write(new Vinyl({
+		base: __dirname,
+		path: __dirname + '/src/conf/ui/app/zebras.xml',
+		contents: new Buffer('zebras')
+	}));
+
+	stream.on('data', function (file) {
+		expect(file.contents.toString()).to.equal(expectedFile);
+		expect(file.path.split(path.sep).pop()).to.equal('library-preload.js');
+	});
+
+	stream.on('end', done);
+	stream.end();
+});
+
+lab.test('creates a library-preload.json file full of unicorns and zebras :-)', function (done) {
+	var stream = ui5Preload({base: 'src/conf/ui', namespace: 'sap.pdms.fdn', isLibrary: true, format: 'json'});
 	var expectedFile = '{\n\t"name": "sap.pdms.fdn.library-preload",\n\t"version": "2.0",\n\t"modules": {\n\t\t"sap/pdms/fdn/app/unicorns.js": "unicorns",\n\t\t\"sap/pdms/fdn/app/zebras.xml": "zebras"\n\t}\n}';
 
 	stream.write(new Vinyl({
@@ -54,3 +79,53 @@ lab.test('creates a library-preload file full of unicorns and zebras :-)', funct
 	stream.on('end', done);
 	stream.end();
 });
+
+lab.test('creates a foo.js file full of unicorns and zebras :-)', function (done) {
+	var stream = ui5Preload({base: 'src/conf/ui', namespace: 'sap.pdms.fdn', isLibrary: true, fileName: 'foo.js'});
+	var expectedFile = 'jQuery.sap.registerPreloadedModules({\n\t"name": "sap.pdms.fdn.library-preload",\n\t"version": "2.0",\n\t"modules": {\n\t\t"sap/pdms/fdn/app/unicorns.js": "unicorns",\n\t\t\"sap/pdms/fdn/app/zebras.xml": "zebras"\n\t}\n});';
+
+	stream.write(new Vinyl({
+		base: __dirname,
+		path: __dirname + '/src/conf/ui/app/unicorns.js',
+		contents: new Buffer('unicorns')
+	}));
+
+	stream.write(new Vinyl({
+		base: __dirname,
+		path: __dirname + '/src/conf/ui/app/zebras.xml',
+		contents: new Buffer('zebras')
+	}));
+
+	stream.on('data', function (file) {
+		expect(file.contents.toString()).to.equal(expectedFile);
+		expect(file.path.split(path.sep).pop()).to.equal('foo.js');
+	});
+
+	stream.on('end', done);
+	stream.end();
+});
+
+lab.test('creates a foo.json file full of unicorns and zebras :-)', function (done) {
+	var stream = ui5Preload({base: 'src/conf/ui', namespace: 'sap.pdms.fdn', isLibrary: true, fileName: 'foo.json'});
+	var expectedFile = '{\n\t"name": "sap.pdms.fdn.library-preload",\n\t"version": "2.0",\n\t"modules": {\n\t\t"sap/pdms/fdn/app/unicorns.js": "unicorns",\n\t\t\"sap/pdms/fdn/app/zebras.xml": "zebras"\n\t}\n}';
+
+	stream.write(new Vinyl({
+		base: __dirname,
+		path: __dirname + '/src/conf/ui/app/unicorns.js',
+		contents: new Buffer('unicorns')
+	}));
+
+	stream.write(new Vinyl({
+		base: __dirname,
+		path: __dirname + '/src/conf/ui/app/zebras.xml',
+		contents: new Buffer('zebras')
+	}));
+
+	stream.on('data', function (file) {
+		expect(file.contents.toString()).to.equal(expectedFile);
+		expect(file.path.split(path.sep).pop()).to.equal('foo.json');
+	});
+
+	stream.on('end', done);
+	stream.end();
+});