diff --git a/.github/workflows/trigger_ab_tests.yml b/.github/workflows/trigger_ab_tests.yml
index 063792ede01d..f6129f956c95 100644
--- a/.github/workflows/trigger_ab_tests.yml
+++ b/.github/workflows/trigger_ab_tests.yml
@@ -14,7 +14,7 @@ jobs:
                -H 'Authorization: Bearer ${{ secrets.BUILDKITE_TOKEN }}' \
                -d '{
                     "commit": "HEAD",
-                    "branch": "${{ toJson(github.event.ref) }}",
+                    "branch": "${{ github.event.ref }}",
                     "env": {
                       "REVISION_A": "${{ github.event.before }}",
                       "REVISION_B": "${{ github.event.after }}"