diff --git a/src/repository/api/ArcanistMercurialAPI.php b/src/repository/api/ArcanistMercurialAPI.php
index 6fecb573..00371d95 100644
--- a/src/repository/api/ArcanistMercurialAPI.php
+++ b/src/repository/api/ArcanistMercurialAPI.php
@@ -101,7 +101,7 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
     if (empty($this->relativeCommit)) {
 
       if ($this->getBaseCommitArgumentRules() ||
-          $this->getWorkingCopyIdentity->getConfigFromAnySource('base')) {
+          $this->getWorkingCopyIdentity()->getConfigFromAnySource('base')) {
         $base = $this->resolveBaseCommit();
         if (!$base) {
           throw new ArcanistUsageException(