diff --git a/python/sglang/srt/managers/scheduler_update_weights_mixin.py b/python/sglang/srt/managers/scheduler_update_weights_mixin.py
index 4a5694571..1fde62ff1 100644
--- a/python/sglang/srt/managers/scheduler_update_weights_mixin.py
+++ b/python/sglang/srt/managers/scheduler_update_weights_mixin.py
@@ -106,6 +106,10 @@ class SchedulerUpdateWeightsMixin:
     def release_memory_occupation(
         self: Scheduler, recv_req: ReleaseMemoryOccupationReqInput
     ):
+        assert (
+            self._is_no_request()
+        ), "release_memory_occupation should be called only when no ongoing request."
+
         tags = recv_req.tags
 
         if tags is None or len(tags) == 0: