diff --git a/qlib/workflow/task/utils.py b/qlib/workflow/task/utils.py
index 4b4a7c06b8e..15a9c083a82 100644
--- a/qlib/workflow/task/utils.py
+++ b/qlib/workflow/task/utils.py
@@ -226,7 +226,7 @@ def truncate(self, segment: tuple, test_start, days: int) -> tuple:
             new_seg = []
             for time_point in segment:
                 tp_idx = min(self.align_idx(time_point), test_idx - days)
-                assert tp_idx > 0
+                assert tp_idx >= 0
                 new_seg.append(self.get(tp_idx))
             return tuple(new_seg)
         else: