diff --git a/clearml/automation/optimization.py b/clearml/automation/optimization.py
index 8787357a..ac01f74e 100644
--- a/clearml/automation/optimization.py
+++ b/clearml/automation/optimization.py
@@ -909,7 +909,7 @@ class HyperParameterOptimizer(object):
             objective_metric_title,  # type: str
             objective_metric_series,  # type: str
             objective_metric_sign='min',  # type: str
-            optimizer_class=RandomSearch,  # type: type(SearchStrategy)
+            optimizer_class=RandomSearch,  # type: Union[SearchStrategy, type(SearchStrategy)]
             max_number_of_concurrent_tasks=10,  # type: int
             execution_queue='default',  # type: str
             optimization_time_limit=None,  # type: Optional[float]