diff --git a/optuna_dashboard/preferential/samplers/gp.py b/optuna_dashboard/preferential/samplers/gp.py
index 188432b8..f56fbdeb 100644
--- a/optuna_dashboard/preferential/samplers/gp.py
+++ b/optuna_dashboard/preferential/samplers/gp.py
@@ -404,7 +404,7 @@ class PreferentialGPSampler(optuna.samplers.BaseSampler):
             is_all_discrete = all(
                 len(possible_params) > 0 for possible_params in all_possible_params.values()
             )
-            search_space_size = np.prod(
+            search_space_size = math.prod(  # Don't use np.prod to avoid overflow
                 [len(possible_params) for possible_params in all_possible_params.values()]
             )
             # TODO(contramundum53): Fix this arbitrarily chosen limit.