diff --git a/rllib/execution/replay_ops.py b/rllib/execution/replay_ops.py
index 516505dd1..d2db8f053 100644
--- a/rllib/execution/replay_ops.py
+++ b/rllib/execution/replay_ops.py
@@ -156,7 +156,7 @@ class MixInReplay:
 
     def __call__(self, sample_batch):
         # Put in replay buffer if enabled.
-        self.buffer.add_batch(sample_batch)
+        self.replay_buffer.add_batch(sample_batch)
 
         # Proportional replay.
         output_batches = [sample_batch]