diff --git a/test/test_envs.py b/test/test_envs.py
index 7c9a619e7d5..92b3f67d11f 100644
--- a/test/test_envs.py
+++ b/test/test_envs.py
@@ -179,7 +179,6 @@ def check_no_lingering_multiprocessing_resources(request):
         _make_envs,
         CARTPOLE_VERSIONED,
         check_rollout_consistency_multikey_env,
-        decorate_thread_sub_func,
         get_default_devices,
         HALFCHEETAH_VERSIONED,
         PENDULUM_VERSIONED,
@@ -191,7 +190,6 @@ def check_no_lingering_multiprocessing_resources(request):
         _make_envs,
         CARTPOLE_VERSIONED,
         check_rollout_consistency_multikey_env,
-        decorate_thread_sub_func,
         get_default_devices,
         HALFCHEETAH_VERSIONED,
         PENDULUM_VERSIONED,
@@ -3405,25 +3403,23 @@ class TestLibThreading:
     )
     def test_num_threads(self):
         gc.collect()
-        from torchrl.envs import batched_envs
-
-        _run_worker_pipe_shared_mem_save = batched_envs._run_worker_pipe_shared_mem
-        batched_envs._run_worker_pipe_shared_mem = decorate_thread_sub_func(
-            batched_envs._run_worker_pipe_shared_mem, num_threads=3
-        )
         num_threads = torch.get_num_threads()
         try:
-            env = ParallelEnv(
-                2, ContinuousActionVecMockEnv, num_sub_threads=3, num_threads=7
-            )
+            # Wrap the env factory to check thread count inside the subprocess.
+            # The env is created AFTER torch.set_num_threads() is called in the worker.
+            def make_env():
+                assert (
+                    torch.get_num_threads() == 3
+                ), f"Expected 3 threads, got {torch.get_num_threads()}"
+                return ContinuousActionVecMockEnv()
+
+            env = ParallelEnv(2, make_env, num_sub_threads=3, num_threads=7)
             # We could test that the number of threads isn't changed until we start the procs.
             # Even though it's unlikely that we have 7 threads, we still disable this for safety
             # assert torch.get_num_threads() != 7
             env.rollout(3)
             assert torch.get_num_threads() == 7
         finally:
-            # reset vals
-            batched_envs._run_worker_pipe_shared_mem = _run_worker_pipe_shared_mem_save
             torch.set_num_threads(num_threads)
 
     @pytest.mark.skipif(