diff --git a/notebooks/AGIPD/Characterize_AGIPD_Gain_Darks_NBC.ipynb b/notebooks/AGIPD/Characterize_AGIPD_Gain_Darks_NBC.ipynb
index 52b639be6ccbc481a69df0242d96ca1441b09306..d42fa752d9c8002af3411e83a83e1f2c31eee6f0 100644
--- a/notebooks/AGIPD/Characterize_AGIPD_Gain_Darks_NBC.ipynb
+++ b/notebooks/AGIPD/Characterize_AGIPD_Gain_Darks_NBC.ipynb
@@ -513,7 +513,15 @@
     "            ga_slice = ga[..., cell_slice_index]\n",
     "            gains[..., cell_number] = np.median(ga_slice, axis=2)\n",
     "            gains_std[..., cell_number] = np.std(ga_slice, axis=2)\n",
-    "    context.map(process_cell, np.unique(cell_ids))\n",
+    "    unique_cell_ids = np.unique(cell_ids)\n",
+    "\n",
+    "    # We assume cells are accepted starting 0.\n",
+    "    if np.any(unique_cell_ids > mem_cells):\n",
+    "        raise ValueError(\n",
+    "            f\"Invalid cells found {unique_cell_ids} \"\n",
+    "            f\"for run: {run_dc.run_metadata()['runNumber']}.\")\n",
+    "\n",
+    "    context.map(process_cell, unique_cell_ids)\n",
     "\n",
     "    # bad pixels\n",
     "    bp = np.zeros_like(offset, dtype=np.uint32)\n",