diff --git a/mmdet/models/losses/triplet_loss.py b/mmdet/models/losses/triplet_loss.py
index d9c9604b8c7..4528239beb4 100644
--- a/mmdet/models/losses/triplet_loss.py
+++ b/mmdet/models/losses/triplet_loss.py
@@ -40,7 +40,7 @@ def hard_mining_triplet_loss_forward(
             inputs (torch.Tensor): feature matrix with shape
                 (batch_size, feat_dim).
             targets (torch.LongTensor): ground truth labels with shape
-                (num_classes).
+                (batch_size).
 
         Returns:
             torch.Tensor: triplet loss with hard mining.