diff --git a/python/paddle/fluid/layers/rnn.py b/python/paddle/fluid/layers/rnn.py
index 079187e09c916a8410448163361c9042d99faaf3..05272a7cefb0827517c22b38b8b85ccdb3036fcc 100644
--- a/python/paddle/fluid/layers/rnn.py
+++ b/python/paddle/fluid/layers/rnn.py
@@ -1395,7 +1395,7 @@ def _dynamic_decode_imperative(decoder,
         control_flow.increment(x=step_idx_tensor, value=1.0, in_place=True)
         step_idx += 1
 
-        control_flow.logical_not(nn.reduce_all(finished), cond)
+        cond = control_flow.logical_not(nn.reduce_all(finished))
         if max_step_num is not None and step_idx > max_step_num:
             break