diff --git a/python-recipes/recommendation-systems/01_collaborative_filtering.ipynb b/python-recipes/recommendation-systems/01_collaborative_filtering.ipynb
index 84165cb..e1abfc6 100644
--- a/python-recipes/recommendation-systems/01_collaborative_filtering.ipynb
+++ b/python-recipes/recommendation-systems/01_collaborative_filtering.ipynb
@@ -251,7 +251,7 @@
    ],
    "source": [
     "# split the data into training and testing sets (80% train, 20% test)\n",
-    "train_set, test_set = train_test_split(ratings_data, test_size=0.2)\n",
+    "train_set, test_set = train_test_split(ratings_data, test_size=0.2, random_state=42)\n",
     "\n",
     "# use SVD (Singular Value Decomposition) for collaborative filtering\n",
     "svd = SVD(n_factors=100, biased=False)  # we'll set biased to False so that predictions are of the form \"rating_prediction = user_vector dot item_vector\"\n",