diff --git a/src/gluonts/testutil/shell.py b/src/gluonts/testutil/shell.py
index 5e1815db6f..c723ae6712 100644
--- a/src/gluonts/testutil/shell.py
+++ b/src/gluonts/testutil/shell.py
@@ -21,7 +21,7 @@
 import typing
 import waitress
 from contextlib import closing, contextmanager
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 from multiprocessing.context import ForkContext
 from pathlib import Path
 from typing import Any, ContextManager, Dict, Iterable, List, Optional, Type
@@ -119,7 +119,7 @@ def free_port() -> int:
 class Server:
     env: ServeEnv
     forecaster_type: Optional[Type[Predictor]]
-    settings: Settings = Settings()
+    settings: Settings = field(default_factory=Settings)
 
     def run(self):
         flask_app = make_flask_app(
diff --git a/test/conftest.py b/test/conftest.py
index b624259a15..8ec8649909 100644
--- a/test/conftest.py
+++ b/test/conftest.py
@@ -30,7 +30,7 @@
 
 try:
     import mxnet as mx
-except ImportError:
+except (ImportError, OSError):
     mx = None
 
 try:
diff --git a/test/core/test_serde_dataclass.py b/test/core/test_serde_dataclass.py
index 324e33c746..f602699711 100644
--- a/test/core/test_serde_dataclass.py
+++ b/test/core/test_serde_dataclass.py
@@ -20,14 +20,13 @@
 @serde.dataclass
 class Estimator:
     prediction_length: int
-    context_length: int = serde.OrElse(
-        lambda prediction_length: prediction_length * 2
-    )
+    context_length: int = serde.EVENTUAL
 
     use_feat_static_cat: bool = True
     cardinality: List[int] = serde.EVENTUAL
 
-    def __eventually__(self, cardinality):
+    def __eventually__(self, context_length, cardinality):
+        context_length.set_default(self.prediction_length * 2)
         if not self.use_feat_static_cat:
             cardinality.set([1])
         else: