diff --git a/src/scitacean/client.py b/src/scitacean/client.py
index d4fd0f08..4519e074 100644
--- a/src/scitacean/client.py
+++ b/src/scitacean/client.py
@@ -778,12 +778,12 @@ def query_datasets(
             )
         """
         # Use a pydantic model to support serializing custom types to JSON.
-        params_model = pydantic.create_model(
+        params_model = pydantic.create_model(  # type: ignore[call-overload]
             "QueryParams", **{key: (type(field), ...) for key, field in fields.items()}
         )
         params = {"fields": params_model(**fields).model_dump_json()}
 
-        limits = {}
+        limits: dict[str, Union[str, int]] = {}
         if order is not None:
             limits["order"] = order
         if limit is not None:
diff --git a/tests/client/query_client_test.py b/tests/client/query_client_test.py
index e9730064..49a97950 100644
--- a/tests/client/query_client_test.py
+++ b/tests/client/query_client_test.py
@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright (c) 2024 SciCat Project (https://github.com/SciCatProject/scitacean)
 
+from typing import Union
+
 import pytest
 from dateutil.parser import parse as parse_datetime
 
@@ -8,7 +10,9 @@
 from scitacean.testing.backend import skip_if_not_backend
 from scitacean.testing.backend.config import SciCatAccess
 
-UPLOAD_DATASETS = {
+UPLOAD_DATASETS: dict[
+    str, Union[model.UploadDerivedDataset, model.UploadRawDataset]
+] = {
     "raw1": model.UploadRawDataset(
         ownerGroup="PLACEHOLDER",
         accessGroups=["uu", "faculty"],