diff --git a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldPHIDs.php b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldPHIDs.php
index 842d662904..d900d41eb3 100644
--- a/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldPHIDs.php
+++ b/src/infrastructure/customfield/standard/PhabricatorStandardCustomFieldPHIDs.php
@@ -1,169 +1,179 @@
 <?php
 
 /**
  * Common code for standard field types which store lists of PHIDs.
  */
 abstract class PhabricatorStandardCustomFieldPHIDs
   extends PhabricatorStandardCustomField {
 
   public function buildFieldIndexes() {
     $indexes = array();
 
     $value = $this->getFieldValue();
     if (is_array($value)) {
       foreach ($value as $phid) {
         $indexes[] = $this->newStringIndex($phid);
       }
     }
 
     return $indexes;
   }
 
   public function readValueFromRequest(AphrontRequest $request) {
     $value = $request->getArr($this->getFieldKey());
     $this->setFieldValue($value);
   }
 
   public function getValueForStorage() {
     $value = $this->getFieldValue();
     if (!$value) {
       return null;
     }
 
     return json_encode(array_values($value));
   }
 
   public function setValueFromStorage($value) {
     $result = array();
     if ($value) {
       $value = json_decode($value, true);
       if (is_array($value)) {
         $result = array_values($value);
       }
     }
     $this->setFieldValue($value);
     return $this;
   }
 
   public function readApplicationSearchValueFromRequest(
     PhabricatorApplicationSearchEngine $engine,
     AphrontRequest $request) {
     return $request->getArr($this->getFieldKey());
   }
 
   public function applyApplicationSearchConstraintToQuery(
     PhabricatorApplicationSearchEngine $engine,
     PhabricatorCursorPagedPolicyAwareQuery $query,
     $value) {
     if ($value) {
       $query->withApplicationSearchContainsConstraint(
         $this->newStringIndex(null),
         $value);
     }
   }
 
   public function getRequiredHandlePHIDsForPropertyView() {
     $value = $this->getFieldValue();
     if ($value) {
       return $value;
     }
     return array();
   }
 
   public function renderPropertyViewValue(array $handles) {
     $value = $this->getFieldValue();
     if (!$value) {
       return null;
     }
 
     $handles = mpull($handles, 'renderLink');
     $handles = phutil_implode_html(', ', $handles);
     return $handles;
   }
 
   public function getRequiredHandlePHIDsForEdit() {
     $value = $this->getFieldValue();
     if ($value) {
       return $value;
     } else {
       return array();
     }
   }
 
   public function getApplicationTransactionRequiredHandlePHIDs(
     PhabricatorApplicationTransaction $xaction) {
 
     $old = json_decode($xaction->getOldValue());
     if (!is_array($old)) {
       $old = array();
     }
 
     $new = json_decode($xaction->getNewValue());
     if (!is_array($new)) {
       $new = array();
     }
 
     $add = array_diff($new, $old);
     $rem = array_diff($old, $new);
 
     return array_merge($add, $rem);
   }
 
   public function getApplicationTransactionTitle(
     PhabricatorApplicationTransaction $xaction) {
     $author_phid = $xaction->getAuthorPHID();
 
     $old = json_decode($xaction->getOldValue());
     if (!is_array($old)) {
       $old = array();
     }
 
     $new = json_decode($xaction->getNewValue());
     if (!is_array($new)) {
       $new = array();
     }
 
     $add = array_diff($new, $old);
     $rem = array_diff($old, $new);
 
     if ($add && !$rem) {
       return pht(
         '%s updated %s, added %d: %s.',
         $xaction->renderHandleLink($author_phid),
         $this->getFieldName(),
         new PhutilNumber(count($add)),
         $xaction->renderHandleList($add));
     } else if ($rem && !$add) {
       return pht(
         '%s updated %s, removed %d: %s.',
         $xaction->renderHandleLink($author_phid),
         $this->getFieldName(),
         new PhutilNumber(count($rem)),
         $xaction->renderHandleList($rem));
     } else {
       return pht(
         '%s updated %s, added %d: %s; removed %d: %s.',
         $xaction->renderHandleLink($author_phid),
         $this->getFieldName(),
         new PhutilNumber(count($add)),
         $xaction->renderHandleList($add),
         new PhutilNumber(count($rem)),
         $xaction->renderHandleList($rem));
     }
   }
 
   public function shouldAppearInHerald() {
     return true;
   }
 
   public function getHeraldFieldConditions() {
     return array(
       HeraldAdapter::CONDITION_INCLUDE_ALL,
       HeraldAdapter::CONDITION_INCLUDE_ANY,
       HeraldAdapter::CONDITION_INCLUDE_NONE,
       HeraldAdapter::CONDITION_EXISTS,
       HeraldAdapter::CONDITION_NOT_EXISTS,
     );
   }
 
+  public function getHeraldFieldValue() {
+    // If the field has a `null` value, make sure we hand an `array()` to
+    // Herald.
+    $value = parent::getHeraldFieldValue();
+    if ($value) {
+      return $value;
+    }
+    return array();
+  }
+
 }