diff --git a/spcd.sh b/spcd.sh
index bb49c9b..7714c83 100644
--- a/spcd.sh
+++ b/spcd.sh
@@ -42,6 +42,8 @@ spcd_main() {
 
 spcd_set_environment_variables() {
 	spcd_step "Set environment variables"
+	# check script first
+	[ -n "${SPCD}" ] || spcd_error_ci "SPCD"
 	# continuous integration / github → gitea → forgejo
 	if [ -n "${GITHUB_ACTIONS}" ]; then
 		# project branch