diff --git a/src/applications/diffusion/query/DiffusionCommitQuery.php b/src/applications/diffusion/query/DiffusionCommitQuery.php
--- a/src/applications/diffusion/query/DiffusionCommitQuery.php
+++ b/src/applications/diffusion/query/DiffusionCommitQuery.php
@@ -439,9 +439,9 @@
     }
 
     if ($this->needIdentities) {
-      $identity_phids = array_merge(
+      $identity_phids = array_unique(array_merge(
         mpull($commits, 'getAuthorIdentityPHID'),
-        mpull($commits, 'getCommitterIdentityPHID'));
+        mpull($commits, 'getCommitterIdentityPHID')));
 
       $data = id(new PhabricatorRepositoryIdentityQuery())
         ->withPHIDs($identity_phids)