diff --git a/gulp/gulp-tests.ts b/gulp/gulp-tests.ts
index 50ebeebf0..0ba2d93d8 100644
--- a/gulp/gulp-tests.ts
+++ b/gulp/gulp-tests.ts
@@ -12,7 +12,15 @@ gulp.task('compile', function()
         .dest('out')
 });
 
-gulp.task('test', ['compile'], function()
+gulp.task('compile2', function(callback: (err?: any) => void)
+{
+    gulp.src("**/*.ts")
+        .pipe(typescript)
+        .dest('out')
+        .on('end', callback);
+});
+
+gulp.task('test', ['compile', 'compile2'], function()
 {
     gulp.src("out/test/**/*.js")
         .pipe(jasmine);
diff --git a/gulp/gulp.d.ts b/gulp/gulp.d.ts
index d12c3edc1..25aa16337 100644
--- a/gulp/gulp.d.ts
+++ b/gulp/gulp.d.ts
@@ -173,15 +173,10 @@ declare module gulp {
     interface ITaskCallback {
         /**
          * Defines a task.
-         * Tasks may be made asynchronous if they return a promise or a stream.
-         */
-        (): any;
-
-        /**
-         * Defines an asynchronous task.
+         * Tasks may be made asynchronous if they are passing a callback or return a promise or a stream.
          * @param cb callback used to signal asynchronous completion. Caller includes <code>err</code> in case of error.
          */
-        (cb:(err?:any)=>void): void;
+        (cb?:(err?:any)=>void): any;
     }
 
     interface EventEmitter {