diff --git a/lib/classes/task/manager.php b/lib/classes/task/manager.php
index a06a4517b49..95cbcfcdf56 100644
--- a/lib/classes/task/manager.php
+++ b/lib/classes/task/manager.php
@@ -135,8 +135,10 @@ class manager {
         global $DB;
 
         $record = self::record_from_adhoc_task($task);
-        // Schedule it immediately.
-        $record->nextruntime = time() - 1;
+        // Schedule it immediately if nextruntime not explicitly set.
+        if (!$task->get_next_run_time()) {
+            $record->nextruntime = time() - 1;
+        }
         $result = $DB->insert_record('task_adhoc', $record);
 
         return $result;
diff --git a/lib/tests/adhoc_task_test.php b/lib/tests/adhoc_task_test.php
index 174e54c2852..1c4d70a0628 100644
--- a/lib/tests/adhoc_task_test.php
+++ b/lib/tests/adhoc_task_test.php
@@ -37,34 +37,76 @@ require_once(__DIR__ . '/fixtures/task_fixtures.php');
  */
 class core_adhoc_task_testcase extends advanced_testcase {
 
-    public function test_get_next_adhoc_task() {
+    /**
+     * Test basic adhoc task execution.
+     */
+    public function test_get_next_adhoc_task_now() {
         $this->resetAfterTest(true);
+
         // Create an adhoc task.
         $task = new \core\task\adhoc_test_task();
 
         // Queue it.
-        $task = \core\task\manager::queue_adhoc_task($task);
+        \core\task\manager::queue_adhoc_task($task);
 
         $now = time();
         // Get it from the scheduler.
         $task = \core\task\manager::get_next_adhoc_task($now);
-        $this->assertNotNull($task);
+        $this->assertInstanceOf('\\core\\task\\adhoc_test_task', $task);
         $task->execute();
+        \core\task\manager::adhoc_task_complete($task);
+    }
 
-        \core\task\manager::adhoc_task_failed($task);
-        // Should not get any task.
+    /**
+     * Test adhoc task failure retry backoff.
+     */
+    public function test_get_next_adhoc_task_fail_retry() {
+        $this->resetAfterTest(true);
+
+        // Create an adhoc task.
+        $task = new \core\task\adhoc_test_task();
+        \core\task\manager::queue_adhoc_task($task);
+
+        $now = time();
+
+        // Get it from the scheduler, execute it, and mark it as failed.
         $task = \core\task\manager::get_next_adhoc_task($now);
-        $this->assertNull($task);
+        $task->execute();
+        \core\task\manager::adhoc_task_failed($task);
+
+        // The task will not be returned immediately.
+        $this->assertNull(\core\task\manager::get_next_adhoc_task($now));
 
         // Should get the adhoc task (retry after delay).
         $task = \core\task\manager::get_next_adhoc_task($now + 120);
-        $this->assertNotNull($task);
+        $this->assertInstanceOf('\\core\\task\\adhoc_test_task', $task);
         $task->execute();
 
         \core\task\manager::adhoc_task_complete($task);
 
         // Should not get any task.
-        $task = \core\task\manager::get_next_adhoc_task($now);
-        $this->assertNull($task);
+        $this->assertNull(\core\task\manager::get_next_adhoc_task($now));
+    }
+
+    /**
+     * Test future adhoc task execution.
+     */
+    public function test_get_next_adhoc_task_future() {
+        $this->resetAfterTest(true);
+
+        $now = time();
+        // Create an adhoc task in future.
+        $task = new \core\task\adhoc_test_task();
+        $task->set_next_run_time($now + 1000);
+        \core\task\manager::queue_adhoc_task($task);
+
+        // Fetching the next task should not return anything.
+        $this->assertNull(\core\task\manager::get_next_adhoc_task($now));
+
+        // Fetching in the future should return the task.
+        $task = \core\task\manager::get_next_adhoc_task($now + 1020);
+        $this->assertInstanceOf('\\core\\task\\adhoc_test_task', $task);
+        $task->execute();
+        \core\task\manager::adhoc_task_complete($task);
     }
 }