diff --git a/cryosparc/api.py b/cryosparc/api.py
index e1f9c1c8..bcbe37c0 100644
--- a/cryosparc/api.py
+++ b/cryosparc/api.py
@@ -7,6 +7,7 @@
 from typing import Any, Callable, ClassVar, Dict, Iterator, List, Optional, Tuple, TypedDict, Union
 
 import httpx
+from pydantic import BaseModel
 
 from . import registry
 from .errors import APIError
@@ -392,9 +393,9 @@ def _decode_json_response(value: Any, schema: dict):
             return model_class(value)
         elif model_class and issubclass(model_class, dict):  # typed dict
             return model_class(**value)
-        elif model_class:  # pydantic model
+        elif model_class and issubclass(model_class, BaseModel):  # pydantic model
             # use model_validate in case validator result derives from subtype, e.g., Event model
-            return model_class.model_validate(value)  # type: ignore
+            return model_class.model_validate(value)
         warnings.warn(
             f"[API] Warning: Received API response with unregistered schema type {schema['$ref']}. "
             "Returning as plain object."
diff --git a/cryosparc/dataset/dtype.py b/cryosparc/dataset/dtype.py
index 3d8811ea..102a697a 100644
--- a/cryosparc/dataset/dtype.py
+++ b/cryosparc/dataset/dtype.py
@@ -35,7 +35,7 @@ class DatasetHeader(TypedDict):
     """Field names that require decompression."""
 
 
-DSET_TO_TYPE_MAP: Dict[DsetType, Type] = {
+DSET_TO_TYPE_MAP: Dict[DsetType, Type[Union[n.number, n.object_]]] = {
     DsetType.T_F32: n.float32,
     DsetType.T_F64: n.float64,
     DsetType.T_C32: n.complex64,
@@ -107,8 +107,10 @@ def get_data_field(data: Data, field: str) -> Field:
 
 def get_data_field_dtype(data: Data, field: str) -> "DTypeLike":
     t = data.type(field)
-    if t == 0 or t not in DSET_TO_TYPE_MAP:
-        raise KeyError(f"Unknown dataset field {field} or field type {t}")
+    if t == 0:
+        raise KeyError(f"Unknown dataset field {field}")
+    elif t not in DSET_TO_TYPE_MAP:
+        raise KeyError(f"Unknown dataset field type {t}")
     dt = n.dtype(DSET_TO_TYPE_MAP[t])
     shape = data.getshp(field)
     return (dt.str, shape) if shape else dt.str
diff --git a/tests/conftest.py b/tests/conftest.py
index 41e7a3e9..b8b46048 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -255,7 +255,13 @@ def mock_api_client_class(mock_user, monkeypatch):
 
 @pytest.fixture
 def cs(mock_api_client_class):
-    return CryoSPARC("https://cryosparc.example.com", email="structura@example.com", password="password")
+    return CryoSPARC(
+        "https://cryosparc.example.com",
+        email="structura@example.com",
+        password="password",
+        host=None,
+        base_port=None,
+    )
 
 
 @pytest.fixture
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 21bde976..6468b3a7 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -31,7 +31,7 @@ def test_cli_login(mock_api_client_class, mock_auth_path):
 
 
 def test_cli_login_auth(mock_user, mock_api_client_class, mock_auth_path):
-    cs = CryoSPARC("https://cryosparc.example.com", email="structura@example.com")
+    cs = CryoSPARC("https://cryosparc.example.com", email="structura@example.com", host=None, base_port=None)
     mock_api_client_class.__call__.assert_called_with(auth="abc123")  # called with token
     assert cs.user == mock_user
     assert cs.test_connection()