diff --git a/lib/xhprof/xhprof_moodle.php b/lib/xhprof/xhprof_moodle.php
index d007eb0edd5..36548eab561 100644
--- a/lib/xhprof/xhprof_moodle.php
+++ b/lib/xhprof/xhprof_moodle.php
@@ -232,7 +232,7 @@ function profiling_stop() {
     }
 
     // If we only profiled because it was potentially slow then...
-    if ($CFG->profilepotentialslowpage) {
+    if (!empty($CFG->profilepotentialslowpage)) {
         $duration = microtime(true) - $CFG->profilepotentialslowpage;
         if ($duration < $CFG->profilingslow) {
             // Wasn't slow enough.