diff --git a/mmcv/ops/sync_bn.py b/mmcv/ops/sync_bn.py
index e8bdd55c7..941910000 100644
--- a/mmcv/ops/sync_bn.py
+++ b/mmcv/ops/sync_bn.py
@@ -126,7 +126,8 @@ class SyncBatchNorm(Module):
         self.momentum = momentum
         self.affine = affine
         self.track_running_stats = track_running_stats
-        self.group = dist.group.WORLD if group is None else group
+        group = dist.group.WORLD if group is None else group
+        self.group = group
         self.group_size = dist.get_world_size(group)
         if self.affine:
             self.weight = Parameter(torch.Tensor(num_features))