diff --git a/bmtrain/block_layer.py b/bmtrain/block_layer.py
index 4e9a6c01..9d852df7 100644
--- a/bmtrain/block_layer.py
+++ b/bmtrain/block_layer.py
@@ -216,7 +216,7 @@ def next_module(self):
         return self._next_module[self._ref_count-1]
 
     def backward_release(self, flag):
-        if self._ref_count == 1:
+        if self._ref_count == 1 and self._backward_block_ctx is not None:
             self._backward_block_ctx.exit(flag, True)
             config['load_stream'].record_event(config['load_event'])
         self._ref_count -= 1