diff --git a/recipe_modules/adhoc_validation/api.py b/recipe_modules/adhoc_validation/api.py
index 7ca0fd9..0d05394 100644
--- a/recipe_modules/adhoc_validation/api.py
+++ b/recipe_modules/adhoc_validation/api.py
@@ -64,6 +64,9 @@
               timeout_secs=4500 # 75 minutes
             )
       else:
+        git_ref = self.m.properties.get('release_ref') or self.m.buildbucket.gitiles_commit.ref
+        # Post-processing of docs require LUCI_BRANCH to be set when running from dart-internal.
+        env['LUCI_BRANCH'] = git_ref.replace('refs/heads/', '')
         # Override LUCI_BRANCH for docs and release candidate branches. Docs built from
         # release candidate branches need to be build as stable to ensure they are processed
         # correctly.