diff --git a/bamt/networks/base.py b/bamt/networks/base.py
index 8090918..eaee66b 100644
--- a/bamt/networks/base.py
+++ b/bamt/networks/base.py
@@ -597,6 +597,7 @@ def fit_parameters(self, data: pd.DataFrame, n_jobs: int = 1):
         """
         Base function for parameter learning
         """
+        data = data.copy()
         if data.isnull().values.any():
             logger_network.error("Dataframe contains NaNs.")
             return