diff --git a/lectures/_static/lecture_specific/inequality/data.ipynb b/lectures/_static/lecture_specific/inequality/data.ipynb
index 1bf3234c..2d9d73b0 100644
--- a/lectures/_static/lecture_specific/inequality/data.ipynb
+++ b/lectures/_static/lecture_specific/inequality/data.ipynb
@@ -85,7 +85,7 @@
     "        # repeat the observations according to their weights\n",
     "        counts = list(round(df[df['year'] == year]['weights'] ))\n",
     "        y = df[df['year'] == year][var].repeat(counts)\n",
-    "        y = np.asarray(y)\n",
+    "        y = np.asarray(y).copy()\n",
     "        \n",
     "        rd.shuffle(y)    # shuffle the sequence\n",
     "      \n",