diff --git a/mmcv/ops/prroi_pool.py b/mmcv/ops/prroi_pool.py
index 8c263e3078..c36661ae4a 100644
--- a/mmcv/ops/prroi_pool.py
+++ b/mmcv/ops/prroi_pool.py
@@ -35,8 +35,8 @@ def forward(ctx,
                 spatial_scale: float = 1.0) -> torch.Tensor:
         if features.dtype != torch.float32 or rois.dtype != torch.float32:
             raise ValueError('Precise RoI Pooling only takes float input, got '
-                             f'{features.dtype()} for features and'
-                             f'{rois.dtype()} for rois.')
+                             f'{features.dtype} for features and'
+                             f'{rois.dtype} for rois.')
 
         pooled_height = int(output_size[0])
         pooled_width = int(output_size[1])