diff --git a/wenet/dataset/datapipes.py b/wenet/dataset/datapipes.py
index 54127a821..dd839f29d 100644
--- a/wenet/dataset/datapipes.py
+++ b/wenet/dataset/datapipes.py
@@ -340,6 +340,7 @@ def __iter__(self):
                 weights[i] = 0.
                 exhausted[i] = True
                 if all(exhausted):
+                    self.iters = None
                     return
                 weights = [weight / sum(weights) for weight in weights]