diff --git a/notebooks/AGIPD/Characterize_AGIPD_Gain_Darks_NBC.ipynb b/notebooks/AGIPD/Characterize_AGIPD_Gain_Darks_NBC.ipynb
index b649d822eb9e1a6e996a9b98d394e8bd96dfdc30..7cd2606bad9bda0c08332878330c344ca2f41cba 100644
--- a/notebooks/AGIPD/Characterize_AGIPD_Gain_Darks_NBC.ipynb
+++ b/notebooks/AGIPD/Characterize_AGIPD_Gain_Darks_NBC.ipynb
@@ -419,7 +419,7 @@
     "            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(num_cells))\n",
+    "    context.map(process_cell, np.unique(cellIds))\n",
     "\n",
     "    # bad pixels\n",
     "    bp = np.zeros_like(offset, dtype=np.uint32)\n",