Output as array works only for 2 formats

[verlok]

Hello,
I'm doing the following:

gulp.task("default", function() {
	process.env.NODE_ENV = "release";
	return (
		gulp.
			src("./src/lazyload.js").
			pipe(sourcemaps.init()).
			// ----------- linting --------------
			pipe(eslint()).
			pipe(eslint.format()).
			pipe(eslint.failAfterError()). // --> failing if errors
			// ----------- rolling up --------------
			pipe(
				rollup({ plugins: [babel()] }, [
					{
						file: "dist/lazyload-es2015.js",
						format: "es"
					},
					{
						file: "dist/lazyload-amd.js",
						format: "amd"
					},
					{
						file: "dist/lazyload-umd.js",
						format: "umd"
					}
				])
			).
			pipe(sourcemaps.write("")).
			pipe(gulp.dest(destFolder))
	);
});

And I noticed that it only outputs the 1st and the 3rd output format.
I've tried to invert the order of the amd and the umd one, and it always outputs the last, ignoring the 2nd.

What am I doing wrong?