diff --git a/transaction_fee_models/simulation.py b/transaction_fee_models/simulation.py
index 71b9805..decaf61 100644
--- a/transaction_fee_models/simulation.py
+++ b/transaction_fee_models/simulation.py
@@ -1,5 +1,6 @@
 from typing import List, Dict, Any, Tuple
 import numpy as np
+np.random.seed(42)
 import pandas as pd
 import tqdm