diff --git a/infra/run-domain-check.sh b/infra/run-domain-check.sh
index 4455ba3..3c360d6 100755
--- a/infra/run-domain-check.sh
+++ b/infra/run-domain-check.sh
@@ -364,7 +364,8 @@ zaak_url_v="$(printf '%s' "$body" | grep -oiE 'http://[^"]*/zaken/api/v1/zaken/[
 echo ">> confirming the zaak $zaak_url_v reached the Geannuleerd status in OpenZaak"
 
 read_zaak_status() {
-  docker run --rm --network "$net" \
+  # -i so the heredoc reaches `python -` on the container's stdin (without it the script is empty).
+  docker run --rm -i --network "$net" \
     -e OZ_CLIENT_ID="${OZ_CLIENT_ID:-big-reference-seed}" \
     -e OZ_SECRET="${OZ_SECRET:-insecure-dev-secret-change-me}" \
     python:3-slim python - "$1" <<'PY'