diff --git a/adit/core/tests/utils/test_dicom_utils.py b/adit/core/tests/utils/test_dicom_utils.py
index 2fe924c2..1052aa0d 100644
--- a/adit/core/tests/utils/test_dicom_utils.py
+++ b/adit/core/tests/utils/test_dicom_utils.py
@@ -61,10 +61,20 @@ def test_convert_to_python_date():
     assert convert_to_python_date("20230831") == date(2023, 8, 31)
 
 
+def test_convert_to_python_date_rejects_empty_value():
+    with pytest.raises(ValueError):
+        convert_to_python_date("")
+
+
 def test_convert_to_python_time():
     assert convert_to_python_time("080000") == time(8, 0, 0)
 
 
+def test_convert_to_python_time_rejects_empty_value():
+    with pytest.raises(ValueError):
+        convert_to_python_time("")
+
+
 def test_convert_to_python_regex_exact_match():
     # No wildcard = exact whole-value match (DICOM Single Value Matching)
     pattern = convert_to_python_regex("query")
diff --git a/adit/core/utils/dicom_utils.py b/adit/core/utils/dicom_utils.py
index 9f60e47d..5c5703d8 100644
--- a/adit/core/utils/dicom_utils.py
+++ b/adit/core/utils/dicom_utils.py
@@ -143,16 +143,24 @@ def convert_to_dicom_datetime(value: str | datetime.datetime | DateTimeRange) ->
 
 
 def convert_to_python_date(value: str) -> datetime.date:
-    """Convert a DICOM date string to a Python date object."""
+    """Convert a DICOM date string to a Python date object.
+
+    Raises ValueError if the value is empty or invalid.
+    """
     date_valuerep = valuerep.DA(value)
-    assert date_valuerep is not None
+    if date_valuerep is None:
+        raise ValueError(f"Empty DICOM date: {value!r}")
     return datetime.date.fromisoformat(date_valuerep.isoformat())
 
 
 def convert_to_python_time(value: str) -> datetime.time:
-    """Convert a DICOM date string to a Python date object."""
+    """Convert a DICOM time string to a Python time object.
+
+    Raises ValueError if the value is empty or invalid.
+    """
     time_valuerep = valuerep.TM(value)
-    assert time_valuerep is not None
+    if time_valuerep is None:
+        raise ValueError(f"Empty DICOM time: {value!r}")
     return datetime.time.fromisoformat(time_valuerep.isoformat())
 
 
diff --git a/adit/mass_transfer/tests/test_processor.py b/adit/mass_transfer/tests/test_processor.py
index b662f98b..0631e38b 100644
--- a/adit/mass_transfer/tests/test_processor.py
+++ b/adit/mass_transfer/tests/test_processor.py
@@ -699,8 +699,17 @@ def test_discover_series_exclude_by_institution(mocker: MockerFixture):
     assert series_uids == {"1.2.3.901"}
 
 
-def test_discover_series_salvages_malformed_study_time(mocker: MockerFixture):
-    """A non-conformant StudyTime (as returned by some PACS) falls back to midnight."""
+@pytest.mark.parametrize(
+    "study_time",
+    [
+        # TM only allows a fractional part after full HHMMSS, so HHMM.fff is invalid
+        pytest.param("1113.672", id="non-conformant"),
+        # StudyTime is Type 2, so a PACS may return it empty
+        pytest.param("", id="empty"),
+    ],
+)
+def test_discover_series_salvages_unparseable_study_time(mocker: MockerFixture, study_time: str):
+    """A StudyTime that can't be parsed (as returned by some PACS) falls back to midnight."""
     processor = _make_processor(mocker)
     processor.mass_task.partition_start = datetime(2024, 1, 1, 0, 0)
     processor.mass_task.partition_end = datetime(2024, 1, 1, 23, 59, 59)
@@ -709,8 +718,7 @@ def test_discover_series_salvages_malformed_study_time(mocker: MockerFixture):
     operator.server = mocker.MagicMock(max_search_results=200)
 
     study = _make_study("1.2.3.100")
-    # TM only allows a fractional part after full HHMMSS, so HHMM.fff is invalid
-    _set_nonconformant(study.dataset, "StudyTime", "1113.672")
+    _set_nonconformant(study.dataset, "StudyTime", study_time)
     operator.find_studies.return_value = [study]
     operator.find_series.return_value = [_make_series_result("1.2.3.201")]