diff --git a/src/applications/differential/harbormaster/DifferentialBuildableEngine.php b/src/applications/differential/harbormaster/DifferentialBuildableEngine.php
index 8554f7be25..8565c2dcad 100644
--- a/src/applications/differential/harbormaster/DifferentialBuildableEngine.php
+++ b/src/applications/differential/harbormaster/DifferentialBuildableEngine.php
@@ -1,81 +1,85 @@
 <?php
 
 final class DifferentialBuildableEngine
   extends HarbormasterBuildableEngine {
 
   protected function getPublishableObject() {
     $object = $this->getObject();
 
     if ($object instanceof DifferentialDiff) {
-      return $object->getRevision();
+      if ($object->getRevisionID()) {
+        return $object->getRevision();
+      } else {
+        return null;
+      }
     }
 
     return $object;
   }
 
   public function publishBuildable(
     HarbormasterBuildable $old,
     HarbormasterBuildable $new) {
 
     // If we're publishing to a diff that is not actually attached to a
     // revision, we have nothing to publish to, so just bail out.
     $revision = $this->getPublishableObject();
     if (!$revision) {
       return;
     }
 
     // Don't publish manual buildables.
     if ($new->getIsManualBuildable()) {
       return;
     }
 
     // Don't publish anything if the buildable is still building. Differential
     // treats more buildables as "building" than Harbormaster does, but the
     // Differential definition is a superset of the Harbormaster definition.
     if ($new->isBuilding()) {
       return;
     }
 
     $viewer = $this->getViewer();
 
     $old_status = $revision->getBuildableStatus($new->getPHID());
     $new_status = $revision->newBuildableStatus($viewer, $new->getPHID());
     if ($old_status === $new_status) {
       return;
     }
 
     $buildable_type = DifferentialRevisionBuildableTransaction::TRANSACTIONTYPE;
 
     $xaction = $this->newTransaction()
       ->setMetadataValue('harbormaster:buildablePHID', $new->getPHID())
       ->setTransactionType($buildable_type)
       ->setNewValue($new_status);
 
     $this->applyTransactions(array($xaction));
   }
 
   public function getAuthorIdentity() {
     $object = $this->getObject();
 
     if ($object instanceof DifferentialRevision) {
       $object = $object->loadActiveDiff();
     }
 
     $authorship = $object->getDiffAuthorshipDict();
     if (!isset($authorship['authorName'])) {
       return null;
     }
 
     $name = $authorship['authorName'];
     $address = idx($authorship, 'authorEmail');
 
     $full = id(new PhutilEmailAddress())
       ->setDisplayName($name)
       ->setAddress($address);
 
     return id(new PhabricatorRepositoryIdentity())
       ->setIdentityName((string)$full)
       ->makeEphemeral();
   }
 
 }