diff --git a/mmdet/datasets/coco.py b/mmdet/datasets/coco.py
index cb69b8e0b081e83de23055f823bae8e9a5a0bbb1..0b3af9bde1e703173d7f8c7d5c98fefe5f61b68f 100644
--- a/mmdet/datasets/coco.py
+++ b/mmdet/datasets/coco.py
@@ -40,7 +40,7 @@ class CocoDataset(CustomDataset):
         img_id = self.img_infos[idx]['id']
         ann_ids = self.coco.getAnnIds(imgIds=[img_id])
         ann_info = self.coco.loadAnns(ann_ids)
-        return self._parse_ann_info(ann_info,self.with_mask)
+        return self._parse_ann_info(ann_info, self.with_mask)
 
     def _filter_imgs(self, min_size=32):
         """Filter images too small or without ground truths."""