diff --git a/mmdet/models/roi_heads/htc_roi_head.py b/mmdet/models/roi_heads/htc_roi_head.py
index e2d3d7384de..5b5c2ec3bc9 100644
--- a/mmdet/models/roi_heads/htc_roi_head.py
+++ b/mmdet/models/roi_heads/htc_roi_head.py
@@ -536,8 +536,8 @@ def aug_test(self, img_feats, proposal_list, img_metas, rescale=False):
         if self.with_mask:
             if det_bboxes.shape[0] == 0:
                 segm_result = [[[]
-                                for _ in range(self.mask_head[-1].num_classes -
-                                               1)]]
+                                for _ in range(self.mask_head[-1].num_classes)]
+                               ]
             else:
                 aug_masks = []
                 aug_img_metas = []