diff --git a/mmcv/ops/csrc/common/cuda/active_rotated_filter_cuda_kernel.cuh b/mmcv/ops/csrc/common/cuda/active_rotated_filter_cuda_kernel.cuh
index 36e41107eb..2d908f4c52 100644
--- a/mmcv/ops/csrc/common/cuda/active_rotated_filter_cuda_kernel.cuh
+++ b/mmcv/ops/csrc/common/cuda/active_rotated_filter_cuda_kernel.cuh
@@ -21,6 +21,7 @@ __global__ void active_rotated_filter_forward_cuda_kernel(
     int j = (index / nEntry) % num_input_planes;
     int i = index / nEntry / num_input_planes;
     int k;
+    int flag = 1;
     scalar_t val = *(weight_data + index);
     for (k = 0; k < num_rotations; k++) {
       int idx = (int)(*(indices_data + l * num_rotations + k)) - 1;