diff --git a/poisson.py b/poisson.py
index 943ddfecd0447524c310f241766a3bc6d6475934..79881d81014feb4f6b368a9132f5ed39f0f1418a 100644
--- a/poisson.py
+++ b/poisson.py
@@ -37,5 +37,5 @@ def fit(
                 print(f"Save histogram {save_fig_path}")
             except Exception as e:
                 print("saving histogram failed", e.args)
-        plt.show()
+        plt.close()
     return lambda_fit_result