diff --git a/src/applications/repository/xaction/PhabricatorRepositoryDefaultBranchTransaction.php b/src/applications/repository/xaction/PhabricatorRepositoryDefaultBranchTransaction.php
--- a/src/applications/repository/xaction/PhabricatorRepositoryDefaultBranchTransaction.php
+++ b/src/applications/repository/xaction/PhabricatorRepositoryDefaultBranchTransaction.php
@@ -22,7 +22,7 @@
         '%s removed %s as the default branch.',
         $this->renderAuthor(),
         $this->renderOldValue());
-    } else if (!strlen($old)) {
+    } else if (!phutil_nonempty_string($old)) {
       return pht(
         '%s set the default branch to %s.',
         $this->renderAuthor(),