diff --git a/mmdet/datasets/loader/sampler.py b/mmdet/datasets/loader/sampler.py
index f45ba1325d5ec235d28ec92f460820a3adfee7cf..c222eb293416813f982be06d2a98736eac85f1c4 100644
--- a/mmdet/datasets/loader/sampler.py
+++ b/mmdet/datasets/loader/sampler.py
@@ -67,7 +67,7 @@ class GroupSampler(Sampler):
                 range(len(indices) // self.samples_per_gpu))
         ]
         indices = np.concatenate(indices)
-        indices = torch.from_numpy(indices).long()
+        indices = indices.astype(np.int64).tolist()
         assert len(indices) == self.num_samples
         return iter(indices)