diff --git a/lib/versioned/^4.0.0/log/sync-task.js b/lib/versioned/^4.0.0/log/sync-task.js
index 1932e89c..08b78d44 100644
--- a/lib/versioned/^4.0.0/log/sync-task.js
+++ b/lib/versioned/^4.0.0/log/sync-task.js
@@ -16,6 +16,8 @@ function warn() {
     return tasks[key];
   }).join(', ');
 
+  process.exitCode = 1;
+
   log.warn(
     ansi.red('The following tasks did not complete:'),
     ansi.cyan(taskNames)
diff --git a/test/expected/flags-tasks-json.json b/test/expected/flags-tasks-json.json
index a9842b7e..2bbe3f2c 100644
--- a/test/expected/flags-tasks-json.json
+++ b/test/expected/flags-tasks-json.json
@@ -1 +1 @@
-{"label":"gulp-cli/test/fixtures/gulpfiles","nodes":[{"label":"test1","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"noop","type":"function","nodes":[]}]}]},{"label":"test2","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"test1","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"noop","type":"function","nodes":[]}]}]},{"label":"noop","type":"function","nodes":[]}]}]},{"label":"test3","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"described","type":"function","nodes":[]}]}]},{"label":"test4","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"errorFunction","type":"function","nodes":[]},{"label":"anon","type":"function","nodes":[]}]}]},{"label":"test5","nodes":[],"type":"task"},{"label":"test6","nodes":[],"type":"task"},{"label":"default","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"test1","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"noop","type":"function","nodes":[]}]}]},{"label":"test3","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"described","type":"function","nodes":[]}]}]},{"label":"noop","type":"function","nodes":[]}]}]}]}
+{"label":"gulp-cli/test/fixtures/gulpfiles","nodes":[{"label":"test1","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"noop","type":"function","nodes":[]}]}]},{"label":"test2","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"test1","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"noop","type":"function","nodes":[]}]}]},{"label":"noop","type":"function","nodes":[]}]}]},{"label":"test3","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"described","type":"function","nodes":[]}]}]},{"label":"test4","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"errorFunction","type":"function","nodes":[]},{"label":"anon","type":"function","nodes":[]}]}]},{"label":"test5","nodes":[],"type":"task"},{"label":"test6","nodes":[],"type":"task"},{"label":"test7","nodes":[],"type":"task"},{"label":"test8","nodes":[],"type":"task"},{"label":"default","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"test1","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"noop","type":"function","nodes":[]}]}]},{"label":"test3","type":"task","nodes":[{"label":"<series>","type":"function","branch":true,"nodes":[{"label":"described","type":"function","nodes":[]}]}]},{"label":"noop","type":"function","nodes":[]}]}]}]}
diff --git a/test/expected/flags-tasks-simple.txt b/test/expected/flags-tasks-simple.txt
index 94ac6fcf..753dbd5d 100644
--- a/test/expected/flags-tasks-simple.txt
+++ b/test/expected/flags-tasks-simple.txt
@@ -4,4 +4,6 @@ test3
 test4
 test5
 test6
+test7
+test8
 default
diff --git a/test/expected/flags-tasks.txt b/test/expected/flags-tasks.txt
index 2d940b2e..5100075b 100644
--- a/test/expected/flags-tasks.txt
+++ b/test/expected/flags-tasks.txt
@@ -25,4 +25,6 @@ gulp-cli/test/fixtures/gulpfiles
 │   ├── errorFunction
 │   └── anon
 ├── test5
-└── test6
+├── test6
+├── test7
+└── test8
diff --git a/test/fixtures/gulpfiles/gulpfile.js b/test/fixtures/gulpfiles/gulpfile.js
index c4baaf27..24cbbd5b 100644
--- a/test/fixtures/gulpfiles/gulpfile.js
+++ b/test/fixtures/gulpfiles/gulpfile.js
@@ -20,6 +20,15 @@ function errorFunction() {
 function anon(cb) {
   cb();
 }
+
+function notCompleting1() {
+  // Callback is not called
+}
+
+function notCompleting2() {
+  // Callback is not called
+}
+
 described.description = 'description';
 
 gulp.task('test1', gulp.series(noop));
@@ -28,5 +37,7 @@ gulp.task('test3', gulp.series(described));
 gulp.task('test4', gulp.series(errorFunction, anon));
 gulp.task('test5', delayed);
 gulp.task('test6', noop);
+gulp.task('test7', notCompleting1);
+gulp.task('test8', notCompleting2);
 
 gulp.task('default', gulp.series('test1', 'test3', noop));
diff --git a/test/non-completing-tasks.js b/test/non-completing-tasks.js
new file mode 100644
index 00000000..afc36337
--- /dev/null
+++ b/test/non-completing-tasks.js
@@ -0,0 +1,36 @@
+'use strict';
+
+var expect = require('expect');
+var eraseTime = require('gulp-test-tools').eraseTime;
+var runner = require('gulp-test-tools').gulpRunner;
+
+
+describe('sync-task', function() {
+  it('should return error code 1 if any tasks did not complete', function(done) {
+    // The exit code is set to 1 by setting process.exitCode = 1 which is only supported from nodejs 0.11 on
+    if (process.version.slice(0, 5) === 'v0.10') {
+      this.skip();
+    }
+
+    runner({ verbose: false })
+      .chdir('test/fixtures/gulpfiles')
+      .gulp('test6 test7 test8')
+      .run(function(err) {
+        expect(err).toNotEqual(null);
+        expect(err.code).toEqual(1);
+        done();
+      });
+  });
+
+  it('should log tasks which did not complete', function(done) {
+    runner({ verbose: false })
+      .chdir('test/fixtures/gulpfiles')
+      .gulp('test6 test7 test8')
+      .run(function(err, stdout) {
+        var lines = stdout.split('\n');
+        expect(lines.length).toEqual(8);
+        expect(eraseTime(lines[5])).toEqual('The following tasks did not complete: test7, test8');
+        done();
+      });
+  });
+});