diff --git a/.buildkite/scripts/lifecycle/post_build.sh b/.buildkite/scripts/lifecycle/post_build.sh
index b5bdfd751a6e3..446ca4b28c559 100755
--- a/.buildkite/scripts/lifecycle/post_build.sh
+++ b/.buildkite/scripts/lifecycle/post_build.sh
@@ -12,7 +12,7 @@ fi
 ts-node "$(dirname "${0}")/ci_stats_complete.ts"
 
 if [[ "${GITHUB_PR_NUMBER:-}" ]]; then
-  DOCS_CHANGES_URL="https://kibana_$GITHUB_PR_NUMBER}.docs-preview.app.elstc.co/diff"
+  DOCS_CHANGES_URL="https://kibana_bk_$GITHUB_PR_NUMBER}.docs-preview.app.elstc.co/diff"
   DOCS_CHANGES=$(curl --connect-timeout 10 -m 10 -sf "$DOCS_CHANGES_URL" || echo '')
 
   if [[ "$DOCS_CHANGES" && "$DOCS_CHANGES" != "There aren't any differences!" ]]; then