diff --git a/src/applications/diffusion/engine/DiffusionCommitHookEngine.php b/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
--- a/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
+++ b/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
@@ -955,6 +955,7 @@
     } else if ($key_new === null) {
       $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_DELETE;
     } else {
+      $_ENV['HG_PENDING'] = getenv('HG_PENDING');
       list($merge_base_raw) = $this->getRepository()->execxLocalCommand(
         'log --template %s --rev %s',
         '{node}',