diff --git a/src/applications/differential/editor/DifferentialTransactionEditor.php b/src/applications/differential/editor/DifferentialTransactionEditor.php
--- a/src/applications/differential/editor/DifferentialTransactionEditor.php
+++ b/src/applications/differential/editor/DifferentialTransactionEditor.php
@@ -632,6 +632,8 @@
   }
 
   protected function getMailTo(PhabricatorLiskDAO $object) {
+    $this->requireReviewers($object);
+
     $phids = array();
     $phids[] = $object->getAuthorPHID();
     foreach ($object->getReviewers() as $reviewer) {
@@ -645,6 +647,8 @@
   }
 
   protected function newMailUnexpandablePHIDs(PhabricatorLiskDAO $object) {
+    $this->requireReviewers($object);
+
     $phids = array();
 
     foreach ($object->getReviewers() as $reviewer) {
@@ -1737,4 +1741,25 @@
     }
   }
 
+  private function requireReviewers(DifferentialRevision $revision) {
+    if ($revision->hasAttachedReviewers()) {
+      return;
+    }
+
+    $with_reviewers = id(new DifferentialRevisionQuery())
+      ->setViewer($this->getActor())
+      ->needReviewers(true)
+      ->withPHIDs(array($revision->getPHID()))
+      ->executeOne();
+    if (!$with_reviewers) {
+      throw new Exception(
+        pht(
+          'Failed to reload revision ("%s").',
+          $revision->getPHID()));
+    }
+
+    $revision->attachReviewers($with_reviewers->getReviewers());
+  }
+
+
 }
diff --git a/src/applications/differential/storage/DifferentialRevision.php b/src/applications/differential/storage/DifferentialRevision.php
--- a/src/applications/differential/storage/DifferentialRevision.php
+++ b/src/applications/differential/storage/DifferentialRevision.php
@@ -583,6 +583,10 @@
     return $this;
   }
 
+  public function hasAttachedReviewers() {
+    return ($this->reviewerStatus !== self::ATTACHABLE);
+  }
+
   public function getReviewerPHIDs() {
     $reviewers = $this->getReviewers();
     return mpull($reviewers, 'getReviewerPHID');