diff --git a/notebooks/LPD/LPD_Correct_Fast.ipynb b/notebooks/LPD/LPD_Correct_Fast.ipynb
index 4fcd7e16ccbd7b997c6c9f22632d1ae2079caabf..733627b88aafc985a98b7182416f4485f57a30e1 100644
--- a/notebooks/LPD/LPD_Correct_Fast.ipynb
+++ b/notebooks/LPD/LPD_Correct_Fast.ipynb
@@ -511,6 +511,7 @@
     "    parallel_gain_indices = None\n",
     "    \n",
     "    if parallel_gain:\n",
+    "        assert (frame_counts % 3 == 0).all(), 'frame count not divisible by 3 in parallel gain mode;\n",
     "        actual_frame_counts = frame_counts // 3\n",
     "\n",
     "        # Indices map where to find each of the high/medium/low gain images for each actual\n",