diff --git a/lib/db/upgradelib.php b/lib/db/upgradelib.php
index 946689b1b81..7285bcce9f3 100644
--- a/lib/db/upgradelib.php
+++ b/lib/db/upgradelib.php
@@ -551,7 +551,7 @@ function upgrade_fix_block_instance_configuration() {
 
     $sql = "SELECT *
               FROM {block_instances}
-             WHERE configdata <> ''";
+             WHERE " . $DB->sql_isnotempty('block_instances', 'configdata', true, true);
     $blockinstances = $DB->get_recordset_sql($sql);
     foreach ($blockinstances as $blockinstance) {
         $configdata = base64_decode($blockinstance->configdata);
diff --git a/lib/tests/upgradelib_test.php b/lib/tests/upgradelib_test.php
index 5d5cfa2d317..86427bae544 100644
--- a/lib/tests/upgradelib_test.php
+++ b/lib/tests/upgradelib_test.php
@@ -27,6 +27,7 @@ defined('MOODLE_INTERNAL') || die();
 
 global $CFG;
 require_once($CFG->libdir.'/upgradelib.php');
+require_once($CFG->libdir.'/db/upgradelib.php');
 
 /**
  * Tests various classes and functions in upgradelib.php library.