diff --git a/src/applications/repository/xaction/PhabricatorRepositoryCallsignTransaction.php b/src/applications/repository/xaction/PhabricatorRepositoryCallsignTransaction.php
--- a/src/applications/repository/xaction/PhabricatorRepositoryCallsignTransaction.php
+++ b/src/applications/repository/xaction/PhabricatorRepositoryCallsignTransaction.php
@@ -25,7 +25,7 @@
     $old = $this->getOldValue();
     $new = $this->getNewValue();
 
-    if (!strlen($old)) {
+    if (!phutil_nonempty_string($old)) {
       return pht(
         '%s set the callsign for this repository to %s.',
         $this->renderAuthor(),