diff --git a/Console/Command/Task/QueueExampleTask.php b/Console/Command/Task/QueueExampleTask.php
index 882c3e1..4de2bff 100644
--- a/Console/Command/Task/QueueExampleTask.php
+++ b/Console/Command/Task/QueueExampleTask.php
@@ -63,7 +63,7 @@ public function add() {
 		$this->out(' ');
 
 		// Adding a task of type 'example' with no additionally passed data
-		if ($this->QueuedTask->createJob('Example', null)) {
+		if ($this->QueuedTask->createJob('Example', [])) {
 			$this->out(__d('queue', 'OK, job created, now run the worker'));
 		} else {
 			$this->err(__d('queue', 'Could not create Job'));
@@ -76,10 +76,10 @@ public function add() {
  *	This function is executed, when a worker is executing a task.
  *	The return parameter will determine, if the task will be marked completed, or be requeued.
  *
- * @param mixed $data Job data (passed on creation)
+ * @param array $data Job data (passed on creation)
  * @return bool Success
  */
-	public function run($data) {
+	public function run(array $data) : bool {
 		$this->hr();
 		$this->out(__d('queue', 'CakePHP Queue Example task.'));
 		$this->hr();
diff --git a/Model/QueuedTask.php b/Model/QueuedTask.php
index 5d0540b..7825df2 100644
--- a/Model/QueuedTask.php
+++ b/Model/QueuedTask.php
@@ -18,11 +18,11 @@ class QueuedTask extends AppModel {
  * Adds a new Job to the queue.
  *
  * @param string $taskName A queue task name
- * @param mixed $data Any data
- * @param string $notBefore A datetime which indicates when the job may be executed
+ * @param array $data Any data
+ * @param ?string $notBefore A datetime which indicates when the job may be executed
  * @return mixed On success `Model::$data` if its not empty or true, false on failure
  */
-	public function createJob($taskName, $data, $notBefore = null) {
+	public function createJob(string $taskName, array $data, $notBefore = null) {
 		$data = [
 			'task' => $taskName,
 			'data' => serialize($data),
diff --git a/Test/Case/Model/QueuedTaskTest.php b/Test/Case/Model/QueuedTaskTest.php
index ea32035..dab417f 100644
--- a/Test/Case/Model/QueuedTaskTest.php
+++ b/Test/Case/Model/QueuedTaskTest.php
@@ -183,9 +183,9 @@ public function testSequence() {
  * @return void
  */
 	public function testNotBefore() {
-		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', null, '+ 1 Min'));
-		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', null, '+ 1 Day'));
-		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', null, '2009-07-01 12:00:00'));
+		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', [], '+ 1 Min'));
+		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', [], '+ 1 Day'));
+		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', [], '2009-07-01 12:00:00'));
 		$data = $this->QueuedTask->find('all');
 		$this->assertEqual($data[4]['QueuedTask']['not_before'], date('Y-m-d H:i:s', strtotime('+ 1 Min')));
 		$this->assertEqual($data[5]['QueuedTask']['not_before'], date('Y-m-d H:i:s', strtotime('+ 1 Day')));
@@ -212,35 +212,35 @@ public function testNotBeforeOrder() {
 				'retries' => 2
 			]
 		];
-		$this->assertTrue((bool)$this->QueuedTask->createJob('dummytask', null));
-		$this->assertTrue((bool)$this->QueuedTask->createJob('dummytask', null));
+		$this->assertTrue((bool)$this->QueuedTask->createJob('dummytask', []));
+		$this->assertTrue((bool)$this->QueuedTask->createJob('dummytask', []));
 		// Create a task with it's execution target some seconds in the past, so it should jump to the top of the list
-		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', 'three', '- 3 Seconds'));
-		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', 'two', '- 4 Seconds'));
-		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', 'one', '- 5 Seconds'));
+		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', ['three'], '- 3 Seconds'));
+		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', ['two'], '- 4 Seconds'));
+		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', ['one'], '- 5 Seconds'));
 
 		// When usin requestJob, the jobs we just created should be delivered in this order,
 		// NOT the order in which they where created
 		$expected = [
 			[
 				'name' => 'task1',
-				'data' => 'one'
+				'data' => ['one']
 			],
 			[
 				'name' => 'task1',
-				'data' => 'two'
+				'data' => ['two']
 			],
 			[
 				'name' => 'task1',
-				'data' => 'three'
+				'data' => ['three']
 			],
 			[
 				'name' => 'dummytask',
-				'data' => ''
+				'data' => []
 			],
 			[
 				'name' => 'dummytask',
-				'data' => ''
+				'data' => []
 			]
 		];
 
@@ -265,15 +265,15 @@ public function testRequeueAfterTimeout() {
 			]
 		];
 
-		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', '1'));
+		$this->assertTrue((bool)$this->QueuedTask->createJob('task1', ['1']));
 		$tmp = $this->QueuedTask->requestJob($capabilities);
 		$this->assertEqual($tmp['task'], 'task1');
-		$this->assertEqual(unserialize($tmp['data']), '1');
+		$this->assertEqual(unserialize($tmp['data']), ['1']);
 		$this->assertEqual($tmp['failed_count'], '0');
 		sleep(2);
 		$tmp = $this->QueuedTask->requestJob($capabilities);
 		$this->assertEqual($tmp['task'], 'task1');
-		$this->assertEqual(unserialize($tmp['data']), '1');
+		$this->assertEqual(unserialize($tmp['data']), ['1']);
 		$this->assertEqual($tmp['failed_count'], '1');
 		$this->assertEqual($tmp['failure_message'], 'Restart after timeout');
 	}
@@ -284,7 +284,7 @@ public function testRequeueAfterTimeout() {
  * @return void
  */
 	public function testMarkJobFailed() {
-		$this->QueuedTask->createJob('dummytask', null);
+		$this->QueuedTask->createJob('dummytask', []);
 		$id = $this->QueuedTask->id;
 		$expected = 'Timeout: 100';
 		$this->QueuedTask->markJobFailed($id, $expected);