diff --git a/lib/classes/task/manager.php b/lib/classes/task/manager.php
index d4e09f9ac47..d1121728505 100644
--- a/lib/classes/task/manager.php
+++ b/lib/classes/task/manager.php
@@ -66,8 +66,11 @@ class manager {
         foreach ($tasks as $task) {
             $record = (object) $task;
             $scheduledtask = self::scheduled_task_from_record($record);
-            $scheduledtask->set_component($componentname);
-            $scheduledtasks[] = $scheduledtask;
+            // Safety check in case the task in the DB does not match a real class (maybe something was uninstalled).
+            if ($scheduledtask) {
+                $scheduledtask->set_component($componentname);
+                $scheduledtasks[] = $scheduledtask;
+            }
         }
 
         return $scheduledtasks;
@@ -237,6 +240,7 @@ class manager {
             $classname = '\\' . $classname;
         }
         if (!class_exists($classname)) {
+            debugging("Failed to load task: " . $classname, DEBUG_DEVELOPER);
             return false;
         }
         $task = new $classname;
@@ -272,6 +276,7 @@ class manager {
             $classname = '\\' . $classname;
         }
         if (!class_exists($classname)) {
+            debugging("Failed to load task: " . $classname, DEBUG_DEVELOPER);
             return false;
         }
         /** @var \core\task\scheduled_task $task */
@@ -328,7 +333,10 @@ class manager {
         $records = $DB->get_records('task_scheduled', array('componentname' => $componentname), 'classname', '*', IGNORE_MISSING);
         foreach ($records as $record) {
             $task = self::scheduled_task_from_record($record);
-            $tasks[] = $task;
+            // Safety check in case the task in the DB does not match a real class (maybe something was uninstalled).
+            if ($task) {
+                $tasks[] = $task;
+            }
         }
 
         return $tasks;
@@ -362,8 +370,12 @@ class manager {
      */
     public static function get_default_scheduled_task($classname) {
         $task = self::get_scheduled_task($classname);
+        $componenttasks = array();
 
-        $componenttasks = self::load_default_scheduled_tasks_for_component($task->get_component());
+        // Safety check in case no task was found for the given classname.
+        if ($task) {
+            $componenttasks = self::load_default_scheduled_tasks_for_component($task->get_component());
+        }
 
         foreach ($componenttasks as $componenttask) {
             if (get_class($componenttask) == get_class($task)) {
@@ -387,7 +399,10 @@ class manager {
 
         foreach ($records as $record) {
             $task = self::scheduled_task_from_record($record);
-            $tasks[] = $task;
+            // Safety check in case the task in the DB does not match a real class (maybe something was uninstalled).
+            if ($task) {
+                $tasks[] = $task;
+            }
         }
 
         return $tasks;
@@ -418,6 +433,11 @@ class manager {
             if ($lock = $cronlockfactory->get_lock('adhoc_' . $record->id, 10)) {
                 $classname = '\\' . $record->classname;
                 $task = self::adhoc_task_from_record($record);
+                // Safety check in case the task in the DB does not match a real class (maybe something was uninstalled).
+                if (!$task) {
+                    $lock->release();
+                    continue;
+                }
 
                 $task->set_lock($lock);
                 if (!$task->is_blocking()) {
@@ -463,6 +483,11 @@ class manager {
             if ($lock = $cronlockfactory->get_lock(($record->classname), 10)) {
                 $classname = '\\' . $record->classname;
                 $task = self::scheduled_task_from_record($record);
+                // Safety check in case the task in the DB does not match a real class (maybe something was uninstalled).
+                if (!$task) {
+                    $lock->release();
+                    continue;
+                }
 
                 $task->set_lock($lock);
 
diff --git a/lib/tests/scheduled_task_test.php b/lib/tests/scheduled_task_test.php
index c29e7f8d878..bb81535d0a4 100644
--- a/lib/tests/scheduled_task_test.php
+++ b/lib/tests/scheduled_task_test.php
@@ -214,4 +214,32 @@ class core_scheduled_task_testcase extends advanced_testcase {
         $task = \core\task\manager::get_next_scheduled_task($now);
         $this->assertNull($task);
     }
+
+    public function test_get_broken_scheduled_task() {
+        global $DB;
+
+        $this->resetAfterTest(true);
+        // Delete all existing scheduled tasks.
+        $DB->delete_records('task_scheduled');
+        // Add a scheduled task.
+
+        // A broken task that runs all the time.
+        $record = new stdClass();
+        $record->blocking = true;
+        $record->minute = '*';
+        $record->hour = '*';
+        $record->dayofweek = '*';
+        $record->day = '*';
+        $record->month = '*';
+        $record->component = 'test_scheduled_task';
+        $record->classname = '\core\task\scheduled_test_task_broken';
+
+        $DB->insert_record('task_scheduled', $record);
+
+        $now = time();
+        // Should not get any task.
+        $task = \core\task\manager::get_next_scheduled_task($now);
+        $this->assertDebuggingCalled();
+        $this->assertNull($task);
+    }
 }