diff --git a/conversion/merge_sa1b.py b/conversion/merge_sa1b.py
index 40f77f1..ddb8068 100644
--- a/conversion/merge_sa1b.py
+++ b/conversion/merge_sa1b.py
@@ -10,7 +10,7 @@ for i in range(len(annbase['images'])):
 for file_idx in range(1,50):
     ann_i = json.load(open('sa_000{}_joint.json'.format(str(file_idx).zfill(3)),'rb'))
     for i in range(len(ann_i['images'])):
-        ann_i['images'][i]['file_name'] = 'sa_000{}/'.format(str(i).zfill(3)) + ann_i['images'][i]['file_name']
+        ann_i['images'][i]['file_name'] = 'sa_000{}/'.format(str(file_idx).zfill(3)) + ann_i['images'][i]['file_name']
     annbase['images'] += ann_i['images']  
     annbase['annotations'] += ann_i['annotations']