diff --git a/tests/DbTestCase.php b/tests/DbTestCase.php
index 3d528093ace..15a0b1dad04 100644
--- a/tests/DbTestCase.php
+++ b/tests/DbTestCase.php
@@ -347,7 +347,7 @@ protected function initAssetDefinition(
                 'is_active'   => true,
                 'capacities'  => $capacities,
                 'profiles'    => $profiles,
-                'fields_display' => '[]',
+                'fields_display' => [],
             ],
             skip_fields: ['capacities', 'profiles'] // JSON encoded fields cannot be automatically checked
         );