diff --git a/alf/algorithms/rl_algorithm_test.py b/alf/algorithms/rl_algorithm_test.py
index b690098c4..96c1088ca 100644
--- a/alf/algorithms/rl_algorithm_test.py
+++ b/alf/algorithms/rl_algorithm_test.py
@@ -102,6 +102,10 @@ def __init__(self, batch_size, obs_shape=(2, ), reward_dim=1):
             shape=(), dtype='int64', minimum=0, maximum=2)
         self.reset()
 
+    @property
+    def is_tensor_based(self):
+        return True
+
     def observation_spec(self):
         return self._observation_spec