diff --git a/optuna_dashboard/preferential/samplers/gp.py b/optuna_dashboard/preferential/samplers/gp.py
index f56fbdeb6..f0aa2c122 100644
--- a/optuna_dashboard/preferential/samplers/gp.py
+++ b/optuna_dashboard/preferential/samplers/gp.py
@@ -317,7 +317,7 @@ def __init__(
 
         self._rng = np.random.RandomState(seed)
         self.independent_sampler = independent_sampler or optuna.samplers.RandomSampler(
-            seed=self._rng.randint(2**32, dtype=np.int64)
+            seed=self._rng.randint(2**32, dtype=np.int64)  # type: ignore
         )
 
         self._search_space = optuna.search_space.IntersectionSearchSpace()