diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldSelect.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldSelect.php
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldSelect.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldSelect.php
@@ -11,7 +11,7 @@
     $indexes = array();
 
     $value = $this->getFieldValue();
-    if (strlen($value)) {
+    if (($value !== null) && ($value !== '')) {
       $indexes[] = $this->newStringIndex($value);
     }