diff --git a/bionic/cache.py b/bionic/cache.py
index 814ef9e6..24600f8f 100644
--- a/bionic/cache.py
+++ b/bionic/cache.py
@@ -767,10 +767,29 @@ def __init__(self, url):
         self.url = url
         bucket_name, object_prefix = self._bucket_and_object_names_from_url(url)
 
-        logger.info("Initializing GCS client ...")
-        self._client = get_gcs_client_without_warnings()
-        self._bucket = self._client.get_bucket(bucket_name)
+        self._bucket_name = bucket_name
         self._object_prefix = object_prefix
+        self._init_client()
+
+    def __getstate__(self):
+        # Copy the object's state from self.__dict__ which contains
+        # all our instance attributes. Always use the dict.copy()
+        # method to avoid modifying the original state.
+        state = self.__dict__.copy()
+        # Remove the unpicklable entries.
+        del state["_client"]
+        del state["_bucket"]
+        return state
+
+    def __setstate__(self, state):
+        # Restore instance attributes.
+        self.__dict__.update(state)
+        # Restore the client and bucket.
+        self._init_client()
+
+    def _init_client(self):
+        self._client = get_gcs_client_without_warnings()
+        self._bucket = self._client.get_bucket(self._bucket_name)
 
     def blob_from_url(self, url):
         object_name = self._validated_object_name_from_url(url)
diff --git a/bionic/flow.py b/bionic/flow.py
index ee717574..676cc6b4 100644
--- a/bionic/flow.py
+++ b/bionic/flow.py
@@ -45,10 +45,6 @@
     oneline,
 )
 
-import logging
-
-logger = logging.getLogger(__name__)
-
 DEFAULT_PROTOCOL = protos.CombinedProtocol(
     protos.ParquetDataFrameProtocol(),
     protos.ImageProtocol(),
diff --git a/bionic/util.py b/bionic/util.py
index a5cfef13..3f5a11ad 100644
--- a/bionic/util.py
+++ b/bionic/util.py
@@ -13,6 +13,10 @@
 
 from .optdep import import_optional_dependency, oneline
 
+import logging
+
+logger = logging.getLogger(__name__)
+
 
 def n_present(*items):
     "Returns the number of non-None arguments."
@@ -123,6 +127,7 @@ def get_gcs_client_without_warnings(cache_value=True):
         warnings.filterwarnings(
             "ignore", "Your application has authenticated using end user credentials"
         )
+        logger.info("Initializing GCS client ...")
         return gcs.Client()
 
 
diff --git a/tests/conftest.py b/tests/conftest.py
index 658fd65f..d29dbeae 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -19,7 +19,7 @@ def process_executor(request):
         return None
 
     loky = import_optional_dependency("loky", purpose="parallel processing")
-    return loky.get_reusable_executor()
+    return loky.get_reusable_executor(max_workers=1)
 
 
 @pytest.fixture(scope="session")
diff --git a/tests/test_flow/test_persistence_gcs.py b/tests/test_flow/test_persistence_gcs.py
index 3313bf2b..24a2ad9e 100644
--- a/tests/test_flow/test_persistence_gcs.py
+++ b/tests/test_flow/test_persistence_gcs.py
@@ -53,7 +53,6 @@ def gcs_builder(builder, tmp_gcs_url_prefix):
 # place.
 # TODO Now that we have a workspace fixture and cached client initialization,
 # this may not be true anymore.
-@pytest.mark.no_parallel
 def test_gcs_caching(gcs_builder, make_counter):
     # Setup.