diff --git a/lib/setup.php b/lib/setup.php
index 3a4c5532f77..77a317cabf6 100644
--- a/lib/setup.php
+++ b/lib/setup.php
@@ -214,7 +214,7 @@ global $HTTPSPAGEREQUIRED;
 
 
 /// Set error reporting back to normal
-    if (empty($CFG->debug)) {
+    if (!isset($CFG->debug)) { // empty() would override 0 or false from config.php
         $CFG->debug = 7;
     }
     error_reporting($CFG->debug);