diff --git a/phpBB/cron.php b/phpBB/cron.php
index 6de493f0bf..cc5964218a 100644
--- a/phpBB/cron.php
+++ b/phpBB/cron.php
@@ -62,14 +62,11 @@ function do_cron($cron_lock, $run_tasks)
 
 if ($config['use_system_cron'])
 {
-	$use_shutdown_function = false;
-
 	$cron = new phpbb_cron_manager($phpbb_root_path . 'includes/cron/task', $phpEx, $cache->get_driver());
 }
 else
 {
 	$cron_type = request_var('cron_type', '');
-	$use_shutdown_function = (@function_exists('register_shutdown_function')) ? true : false;
 
 	// Comment this line out for debugging so the page does not return an image.
 	output_image();
@@ -95,22 +92,12 @@ if ($cron_lock->acquire())
 			}
 			if ($task->is_ready())
 			{
-				if ($use_shutdown_function && !$task->is_shutdown_function_safe())
-				{
-					$use_shutdown_function = false;
-				}
 				$run_tasks = array($task);
 			}
 		}
 	}
-	if ($use_shutdown_function)
-	{
-		register_shutdown_function('do_cron', $cron_lock, $run_tasks);
-	}
-	else
-	{
-		do_cron($cron_lock, $run_tasks);
-	}
+
+	do_cron($cron_lock, $run_tasks);
 }
 else
 {
diff --git a/phpBB/includes/cron/task/base.php b/phpBB/includes/cron/task/base.php
index 38c0b844d9..9db8e3bd44 100644
--- a/phpBB/includes/cron/task/base.php
+++ b/phpBB/includes/cron/task/base.php
@@ -51,23 +51,4 @@ abstract class phpbb_cron_task_base implements phpbb_cron_task
 	{
 		return true;
 	}
-
-	/**
-	* Returns whether this cron task can be run in shutdown function.
-	*
-	* By the time shutdown sequence invokes a particular piece of code,
-	* resources that that code requires may already be released.
-	* If so, a particular cron task may be marked shutdown function-
-	* unsafe, and it will be executed in normal program flow.
-	*
-	* Generally speaking cron tasks should start off as shutdown function-
-	* safe, and only be marked shutdown function-unsafe if a problem
-	* is discovered.
-	*
-	* @return bool		Whether the cron task is shutdown function-safe.
-	*/
-	public function is_shutdown_function_safe()
-	{
-		return true;
-	}
 }
diff --git a/phpBB/includes/cron/task/core/queue.php b/phpBB/includes/cron/task/core/queue.php
index 0e9de05984..96cade0ce5 100644
--- a/phpBB/includes/cron/task/core/queue.php
+++ b/phpBB/includes/cron/task/core/queue.php
@@ -64,21 +64,4 @@ class phpbb_cron_task_core_queue extends phpbb_cron_task_base
 		global $config;
 		return $config['last_queue_run'] < time() - $config['queue_interval_config'];
 	}
-
-	/**
-	* Returns whether this cron task can be run in shutdown function.
-	*
-	* A user reported that using the mail() function during shutdown
-	* function execution does not work. Therefore if email is delivered
-	* via the mail() function (as opposed to SMTP) queue cron task marks
-	* itself shutdown function-unsafe.
-	*
-	* @return bool
-	*/
-	public function is_shutdown_function_safe()
-	{
-		global $config;
-		// A user reported using the mail() function while using shutdown does not work. We do not want to risk that.
-		return !$config['smtp_delivery'];
-	}
 }
diff --git a/phpBB/includes/cron/task/task.php b/phpBB/includes/cron/task/task.php
index 58c4a96f8e..cceccce44f 100644
--- a/phpBB/includes/cron/task/task.php
+++ b/phpBB/includes/cron/task/task.php
@@ -45,20 +45,4 @@ interface phpbb_cron_task
 	* @return bool
 	*/
 	public function should_run();
-
-	/**
-	* Returns whether this cron task can be run in shutdown function.
-	*
-	* By the time shutdown sequence invokes a particular piece of code,
-	* resources that that code requires may already be released.
-	* If so, a particular cron task may be marked shutdown function-
-	* unsafe, and it will be executed in normal program flow.
-	*
-	* Generally speaking cron tasks should start off as shutdown function-
-	* safe, and only be marked shutdown function-unsafe if a problem
-	* is discovered.
-	*
-	* @return bool
-	*/
-	public function is_shutdown_function_safe();
 }