diff --git a/osbenchmark/aggregator.py b/osbenchmark/aggregator.py
index 137a237a..37582f4b 100644
--- a/osbenchmark/aggregator.py
+++ b/osbenchmark/aggregator.py
@@ -214,7 +214,7 @@ def calculate_weighted_average(self, task_metrics: Dict[str, List[Any]], iterati
 
         return weighted_metrics
 
-    def calculate_rsd(self, values, metric_name: str):
+    def calculate_rsd(self, values: List[Union[int, float]], metric_name: str):
         if not values:
             raise ValueError(f"Cannot calculate RSD for metric '{metric_name}': empty list of values")
         if len(values) == 1: