diff --git a/tests/test_graphql/test_api_backup.py b/tests/test_graphql/test_api_backup.py
index f78bb59..660df95 100644
--- a/tests/test_graphql/test_api_backup.py
+++ b/tests/test_graphql/test_api_backup.py
@@ -31,7 +31,7 @@ allSnapshots {
 """
 
 API_BACK_UP_MUTATION = """
-mutation TestBackupService($service_id: String) {
+mutation TestBackupService($service_id: String!) {
         startBackup(serviceId: $service_id) {
             success
             message