diff --git a/admin/tool/monitor/tests/eventobservers_test.php b/admin/tool/monitor/tests/eventobservers_test.php
index 73b684ffb63..79356c6ba5f 100644
--- a/admin/tool/monitor/tests/eventobservers_test.php
+++ b/admin/tool/monitor/tests/eventobservers_test.php
@@ -404,12 +404,11 @@ class tool_monitor_eventobservers_testcase extends advanced_testcase {
      * Run adhoc tasks.
      */
     protected function run_adhock_tasks() {
-        ob_start();
         while ($task = \core\task\manager::get_next_adhoc_task(time())) {
             $task->execute();
             \core\task\manager::adhoc_task_complete($task);
         }
-        ob_clean(); // Suppress mtrace debugging info.
+        $this->expectOutputRegex("/^Sending message to the user with id \d+ for the subscription with id \d+\.\.\..Sent./ms");
     }
 
     /**