diff --git a/python/dgl/contrib/sampling/sampler.py b/python/dgl/contrib/sampling/sampler.py
index aaf441e51aef..b616780acca6 100644
--- a/python/dgl/contrib/sampling/sampler.py
+++ b/python/dgl/contrib/sampling/sampler.py
@@ -554,10 +554,11 @@ def fetch(self, current_index):
             return [subgraph.DGLSubGraph(self.g, subg) for subg in subgs]
         else:
             rets = []
-            assert self._num_workers * 2 == len(subgs)
-            for i in range(self._num_workers):
+            assert len(subgs) % 2 == 0
+            num_pos = int(len(subgs) / 2)
+            for i in range(num_pos):
                 pos_subg = subgraph.DGLSubGraph(self.g, subgs[i])
-                neg_subg = subgraph.DGLSubGraph(self.g, subgs[i + self._num_workers])
+                neg_subg = subgraph.DGLSubGraph(self.g, subgs[i + num_pos])
                 rets.append((pos_subg, neg_subg))
             return rets