diff --git a/src/workflow/ArcanistPatchWorkflow.php b/src/workflow/ArcanistPatchWorkflow.php
--- a/src/workflow/ArcanistPatchWorkflow.php
+++ b/src/workflow/ArcanistPatchWorkflow.php
@@ -296,6 +296,8 @@
       $base_revision = $bundle->getBaseRevision();
 
       if ($base_revision && $has_base_revision) {
+        $base_revision = $repository_api->getCanonicalRevisionName(
+          $base_revision);
         $repository_api->execxLocal(
           'checkout -b %s %s',
           $branch_name,