diff --git a/lib/tests/cronlib_test.php b/lib/tests/cronlib_test.php
index 66b33a99dcd..47ee55cd736 100644
--- a/lib/tests/cronlib_test.php
+++ b/lib/tests/cronlib_test.php
@@ -43,7 +43,7 @@ class cronlib_testcase extends basic_testcase {
         $time = 0;
 
         // Relative time stamps. Did you know data providers get executed during phpunit init?
-        $lastweekstime = strtotime('-1 week') - time();
+        $lastweekstime = -($CFG->tempdatafoldercleanup * 3600); // This must match file_temp_cleanup_task.
         $beforelastweekstime = $lastweekstime - 3600 - 1; // At least 1h and 1s diff (make it DST immune).
         $afterlastweekstime = $lastweekstime + 3600 + 1; // At least 1h and 1s diff (make it DST immune).