diff --git a/src/applications/differential/customfield/DifferentialReviewersField.php b/src/applications/differential/customfield/DifferentialReviewersField.php
index f77f8ab749..41a4cf8f26 100644
--- a/src/applications/differential/customfield/DifferentialReviewersField.php
+++ b/src/applications/differential/customfield/DifferentialReviewersField.php
@@ -237,6 +237,10 @@ final class DifferentialReviewersField
   }
 
   public function validateCommitMessageValue($value) {
+    if (!$value) {
+      return;
+    }
+
     $author_phid = $this->getObject()->getAuthorPHID();
 
     $config_self_accept_key = 'differential.allow-self-accept';