diff --git a/optuna/storages/_rdb/storage.py b/optuna/storages/_rdb/storage.py
index 25d66e6ede..3cb02189cb 100644
--- a/optuna/storages/_rdb/storage.py
+++ b/optuna/storages/_rdb/storage.py
@@ -588,27 +588,14 @@ def _set_trial_param_without_commit(
         trial = models.TrialModel.find_or_raise_by_id(trial_id, session)
         self.check_trial_is_updatable(trial_id, trial.state)
 
-        trial_param = models.TrialParamModel.find_by_trial_and_param_name(
-            trial, param_name, session
+        trial_param = models.TrialParamModel(
+            trial_id=trial_id,
+            param_name=param_name,
+            param_value=param_value_internal,
+            distribution_json=distributions.distribution_to_json(distribution),
         )
 
-        if trial_param is not None:
-            # Raise error in case distribution is incompatible.
-            distributions.check_distribution_compatibility(
-                distributions.json_to_distribution(trial_param.distribution_json), distribution
-            )
-
-            trial_param.param_value = param_value_internal
-            trial_param.distribution_json = distributions.distribution_to_json(distribution)
-        else:
-            trial_param = models.TrialParamModel(
-                trial_id=trial_id,
-                param_name=param_name,
-                param_value=param_value_internal,
-                distribution_json=distributions.distribution_to_json(distribution),
-            )
-
-            trial_param.check_and_add(session)
+        trial_param.check_and_add(session)
 
     def _check_and_set_param_distribution(
         self,
diff --git a/tests/storages_tests/test_storages.py b/tests/storages_tests/test_storages.py
index bf9e3e5da7..5d7cbebd19 100644
--- a/tests/storages_tests/test_storages.py
+++ b/tests/storages_tests/test_storages.py
@@ -486,11 +486,6 @@ def test_set_trial_param(storage_mode: str) -> None:
         # Check set_param breaks neither get_trial nor get_trial_params.
         assert storage.get_trial(trial_id_1).params == {"x": 0.5, "y": "Meguro"}
         assert storage.get_trial_params(trial_id_1) == {"x": 0.5, "y": "Meguro"}
-        # Duplicated registration should overwrite.
-        storage.set_trial_param(trial_id_1, "x", 0.6, distribution_x)
-        assert storage.get_trial_param(trial_id_1, "x") == 0.6
-        assert storage.get_trial(trial_id_1).params == {"x": 0.6, "y": "Meguro"}
-        assert storage.get_trial_params(trial_id_1) == {"x": 0.6, "y": "Meguro"}
 
         # Set params to another trial.
         storage.set_trial_param(trial_id_2, "x", 0.3, distribution_x)