diff --git a/probabilistic-analysis/probabilistic_assessment.py b/probabilistic-analysis/probabilistic_assessment.py
index 60fcd0a..848c4ca 100644
--- a/probabilistic-analysis/probabilistic_assessment.py
+++ b/probabilistic-analysis/probabilistic_assessment.py
@@ -471,7 +471,7 @@ def process(beach_name, beach_scenario, n_runs, start_year, end_year,
                 pbar_year.set_description('Year: {}'.format(year))
 
                 # Create output dataframe
-                df_out = df_in[['beach', 'block', 'profile']]
+                df_out = df_in[['beach', 'block', 'profile']].copy()
                 df_out['block'] = df_out['block'].astype(str)
 
                 # Add info on non-erodable sections