diff --git a/tests/test_TFNetworkRecLayer.py b/tests/test_TFNetworkRecLayer.py
index 6db0e3d6b4..8b4ed3d592 100644
--- a/tests/test_TFNetworkRecLayer.py
+++ b/tests/test_TFNetworkRecLayer.py
@@ -3361,12 +3361,14 @@ def check_reclayer_optimize_out(subnet_layer_dict, other_subnet_layers=None, sha
   with make_scope() as session:
     print("Create non-optimized rec layer (with subnet layer moved out)")
     rec_layer_dict["optimize_move_layers_out"] = False
+    rec_layer_dict["unit"]["window"]["class"] = "slice_nd"
     net1 = TFNetwork(config=config, train_flag=True, name="<root_not_opt>")
     if shared_base_net:
       net1.construct_from_dict(shared_base_net)
       for key in shared_base_net:
         assert key in net1.layers
     net1.construct_from_dict({"output_not_opt": rec_layer_dict})
+    rec_layer_dict["unit"]["window"]["class"] = "slice_nd2"
     rec_layer_dict["optimize_move_layers_out"] = True
     print("Create optimized rec layer (with subnet layer inside loop)")
     net2 = TFNetwork(config=config, extern_data=net1.extern_data, train_flag=True, name="<root_opt>")
@@ -3611,7 +3613,7 @@ def random_start_positions(source, **kwargs):
     from_="position",
     other_subnet_layers={
       "my_layer": {"class": "gather_nd", "from": "base:data", "position": ":i"},
-      "window": {"class": "slice_nd2",    # no_opt: [B,4,D], opt: [B,T,4,D]
+      "window": {"class": "slice_nd",    # no_opt: [B,4,D], opt: [B,T,4,D]
                  "from": "base:data", "start": "data:source", "size": 4, "is_output_layer": True},
       },
     shared_base_net={