diff --git a/cvat/apps/dataset_manager/task.py b/cvat/apps/dataset_manager/task.py
index 1adf5ec5da12..72aaccc50695 100644
--- a/cvat/apps/dataset_manager/task.py
+++ b/cvat/apps/dataset_manager/task.py
@@ -1196,6 +1196,7 @@ def convert_annotation_data_format(data, format_name):
             formatted_data.append(formatted_entry)
         return formatted_data
     elif format_name == "LibriVox":
+        language_id_mapping = {"en": 0}
         formatted_data = []
         for entry in data:
             formatted_entry = {