diff --git a/monai/visualize/occlusion_sensitivity.py b/monai/visualize/occlusion_sensitivity.py
index 6dc4de154f..bb9ef59e5c 100644
--- a/monai/visualize/occlusion_sensitivity.py
+++ b/monai/visualize/occlusion_sensitivity.py
@@ -303,7 +303,8 @@ def __call__(  # type: ignore
 
                 # upsample
                 if self.upsampler is not None:
-                    if np.any(output_im_shape != x.shape[1:]):
+                    assert len(sensitivity_ims_list[i].shape) == len(x.shape)
+                    if np.any(sensitivity_ims_list[i].shape != x.shape):
                         img_spatial = tuple(output_im_shape[1:])
                         sensitivity_ims_list[i] = self.upsampler(img_spatial)(sensitivity_ims_list[i])