diff --git a/src/workflow/ArcanistUpgradeWorkflow.php b/src/workflow/ArcanistUpgradeWorkflow.php
--- a/src/workflow/ArcanistUpgradeWorkflow.php
+++ b/src/workflow/ArcanistUpgradeWorkflow.php
@@ -58,13 +58,14 @@
 
       // Require the library be on master.
       $branch_name = $repository->getBranchName();
-      if ($branch_name != 'master') {
+      if ($branch_name != 'master' && $branch_name != 'stable') {
         throw new ArcanistUsageException(
           pht(
             "%s must be on branch '%s' to be automatically upgraded. ".
-            "This copy of %s (in '%s') is on branch '%s'.",
+            "This copy of %s (in '%s') is on either branch '%s' or '%s'.",
             $lib,
             'master',
+            'stable',
             $lib,
             $root,
             $branch_name));