diff --git a/cwltool/context.py b/cwltool/context.py
index e76c7dad6..28050b8ea 100644
--- a/cwltool/context.py
+++ b/cwltool/context.py
@@ -2,7 +2,6 @@
 import copy
 import os
 import shutil
-import sys
 import tempfile
 import threading
 from typing import (
@@ -199,7 +198,7 @@ def __init__(self, kwargs: Optional[Dict[str, Any]] = None) -> None:
         self.default_stdout: Optional[Union[IO[bytes], TextIO]] = None
         self.default_stderr: Optional[Union[IO[bytes], TextIO]] = None
         self.validate_only: bool = False
-        self.validate_stdout: Union[IO[bytes], TextIO, IO[str]] = sys.stdout
+        self.validate_stdout: Optional[Union[IO[bytes], TextIO, IO[str]]] = None
         super().__init__(kwargs)
         if self.tmp_outdir_prefix == "":
             self.tmp_outdir_prefix = self.tmpdir_prefix
diff --git a/tests/test_subclass_mypyc.py b/tests/test_subclass_mypyc.py
index bb138cdc5..aa4964b34 100644
--- a/tests/test_subclass_mypyc.py
+++ b/tests/test_subclass_mypyc.py
@@ -81,3 +81,12 @@ def test_serialize_builder() -> None:
         "docker",
     )
     assert pickle.dumps(builder)
+
+
+def test_pickle_unpickle_runtime_context() -> None:
+    """We can pickle & unpickle RuntimeContext"""
+
+    runtime_context = RuntimeContext()
+    stream = pickle.dumps(runtime_context)
+    assert stream
+    assert pickle.loads(stream)