diff --git a/tests/framework/ab_test.py b/tests/framework/ab_test.py
index 26bfd3a5ba1e..1fb1e20e2714 100644
--- a/tests/framework/ab_test.py
+++ b/tests/framework/ab_test.py
@@ -40,7 +40,7 @@
 
 # Locally, this will always compare against main, even if we try to merge into, say, a feature branch.
 # We might want to do a more sophisticated way to determine a "parent" branch here.
-DEFAULT_A_REVISION = os.environ.get("BUILDKITE_PULL_REQUEST_BASE_BRANCH", "main")
+DEFAULT_A_REVISION = "origin/" + os.environ.get("BUILDKITE_PULL_REQUEST_BASE_BRANCH", "main")
 
 
 T = TypeVar("T")