diff --git a/module2/exo4/exercice.ipynb b/module2/exo4/exercice.ipynb
index 93e406939262c0cdf8f9964b75af988c9a2c819b..1254812aede97d00b5d68805732ab9357cf9ce6c 100644
--- a/module2/exo4/exercice.ipynb
+++ b/module2/exo4/exercice.ipynb
@@ -2,7 +2,10 @@
  "cells": [
   {
    "cell_type": "markdown",
-   "metadata": {},
+   "metadata": {
+    "hideCode": false,
+    "hidePrompt": false
+   },
    "source": [
     "# Useful links\n",
     "\n",
@@ -17,6 +20,31 @@
     "    - for histogram plots [take this](https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.hist.html)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {
+    "hideCode": false,
+    "hidePrompt": false
+   },
+   "source": [
+    "Exercise 3.2: had a weird error message when trying to execute the evaluation part:\n",
+    "\n",
+    "```\n",
+    "---------------------------------------------------------------------------\n",
+    "AssertionError                            Traceback (most recent call last)\n",
+    "<ipython-input-12-537d91e19818> in <module>\n",
+    "      4                         first_september_week[1:]):\n",
+    "      5     one_year = sorted_data['inc'][week1:week2-1]\n",
+    "----> 6     assert abs(len(one_year)-52) < 2\n",
+    "      7     yearly_incidence.append(one_year.sum())\n",
+    "      8     year.append(week2.year)\n",
+    "\n",
+    "AssertionError: \n",
+    "```\n",
+    "\n",
+    "worked on it together with Eva diaz, trying to figure out what the problem was, but couldn't find any solution... "
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
@@ -26,6 +54,7 @@
   }
  ],
  "metadata": {
+  "hide_code_all_hidden": false,
   "kernelspec": {
    "display_name": "Python 3",
    "language": "python",