diff --git a/extras/opl/horreum_api.py b/extras/opl/horreum_api.py
index f8b4841..9bfddb1 100755
--- a/extras/opl/horreum_api.py
+++ b/extras/opl/horreum_api.py
@@ -182,7 +182,7 @@ def create_label(
             }
 
         url = f"{self.base_url}/api/schema/{schema_id}/labels"
-        response = self.session.post(url, json=label_data)
+        response = self.session.post(url, json=[label_data])
         response.raise_for_status()
         return response.json()