diff --git a/torchsparse/nn/functional/conv/func/implicit_gemm.py b/torchsparse/nn/functional/conv/func/implicit_gemm.py
index e91ad18..c700541 100644
--- a/torchsparse/nn/functional/conv/func/implicit_gemm.py
+++ b/torchsparse/nn/functional/conv/func/implicit_gemm.py
@@ -161,7 +161,7 @@ def backward(ctx, grad_output: torch.Tensor):
                             reorder_out_in_map_bwd,
                             reduced_sorted_mask_bwd_wgrad,
                             reorder_loc_bwd,
-                            32,
+                            1,
                             torchsparse.backends.allow_tf32,
                             torchsparse.backends.allow_fp16,
                             torchsparse.backends.allow_bf16
@@ -192,7 +192,7 @@ def backward(ctx, grad_output: torch.Tensor):
                             grad_output,
                             input,
                             out_in_map_bwd,
-                            32,
+                            1,
                             torchsparse.backends.allow_tf32,
                             torchsparse.backends.allow_fp16,
                             torchsparse.backends.allow_bf16