diff --git a/notebooks/LPD/LPDChar_Darks_NBC.ipynb b/notebooks/LPD/LPDChar_Darks_NBC.ipynb
index 9ba4365fc8dbeb086ce84c31800870f78225a5fc..de76f651d6b3f713b3e96102a8dd793eb850a3d9 100644
--- a/notebooks/LPD/LPDChar_Darks_NBC.ipynb
+++ b/notebooks/LPD/LPDChar_Darks_NBC.ipynb
@@ -183,14 +183,18 @@
     "\n",
     "# the actual characterization\n",
     "def characterize_module(run_path, channel, gg):\n",
-    "    run = RunDirectory(run_path)\n",
+    "    run = RunDirectory(run_path, parallelize=False)\n",
     "    det_source = source_name.format(karabo_id, channel)\n",
     "    data = run[det_source, 'image.data'].drop_empty_trains()\n",
     "    data = data[skip_first_ntrains : skip_first_ntrains + ntrains]\n",
     "    cell_ids = run[det_source, 'image.cellId'].drop_empty_trains()\n",
     "    cell_ids = cell_ids[skip_first_ntrains : skip_first_ntrains + ntrains]\n",
-    "    \n",
-    "    if len(data.train_ids) < min_trains:\n",
+    "\n",
+    "    # If there is no data available, return and expect this\n",
+    "    # module to be skipped later.\n",
+    "    if len(data.train_ids) == 0:\n",
+    "        return None, None, None, None, None, None, None, None\n",
+    "    elif len(data.train_ids) < min_trains:\n",
     "        raise Exception(f\"Run {run_path} only contains {len(data.train_ids)} trains, but {min_trains} required\")\n",
     "\n",
     "    im = data.ndarray()\n",
diff --git a/tests/test_reference_runs/conftest.py b/tests/test_reference_runs/conftest.py
index 19e3d9cdc8d2449b2696b63dd0a83851627fc080..ce3b9745888821e5e75fe4c6ef02e76a35047c56 100644
--- a/tests/test_reference_runs/conftest.py
+++ b/tests/test_reference_runs/conftest.py
@@ -9,9 +9,7 @@ def pytest_addoption(parser):
         default=False,
         help="Start release test for all supported calibration notebooks",
     )
-    # detectors_choices = []
-    # for k in ['agipd', 'jungfrau', 'pnccd', 'epix100', 'all']:
-    #     detectors_choices += [k, k.upper()]
+
     parser.addoption(
         "--detectors",
         default=["all"],
@@ -20,7 +18,7 @@ def pytest_addoption(parser):
 
     parser.addoption(
         "--calibration",
-        type=str,
+        type=str.lower,
         choices=["correct", "dark", "all"],
         default="all",
     )