diff --git a/resource_work_time_from_contracts/tests/test_work_time.py b/resource_work_time_from_contracts/tests/test_work_time.py
index 116f505fa..ff78cd8ec 100644
--- a/resource_work_time_from_contracts/tests/test_work_time.py
+++ b/resource_work_time_from_contracts/tests/test_work_time.py
@@ -3,8 +3,6 @@
 
 from datetime import date, timedelta, timezone
 
-from odoo.addons.test_resource.tests.test_resource import datetime_str
-
 from .test_work_time_base import TestWorkTimeBase
 
 
diff --git a/resource_work_time_from_contracts/tests/test_work_time_base.py b/resource_work_time_from_contracts/tests/test_work_time_base.py
index 4398afed0..acaba1f2c 100644
--- a/resource_work_time_from_contracts/tests/test_work_time_base.py
+++ b/resource_work_time_from_contracts/tests/test_work_time_base.py
@@ -140,6 +140,13 @@ def to_utc_datetime(self, year, month, day, *args, **kwargs):
         """
         Create a UTC datetime from local time values
         """
-        return self.timezone.localize(
-            datetime.datetime(year, month, day, *args, **kwargs)
-        ).astimezone(pytz.utc)
+        return (
+            self.timezone.localize(
+                datetime.datetime(year, month, day, *args, **kwargs)
+            ).astimezone(pytz.utc)
+            # Odoo's ORM refuses to work with datetime objects that have tzinfo
+            # set. Unset it here instead of doing it manually every time. The
+            # tzinfo is implicit as a result of this function's name being
+            # 'to_utc_datetime'.
+            .replace(tzinfo=None)
+        )