diff --git a/pyro_risks/utils/s3.py b/pyro_risks/utils/s3.py
index 8dadd34..d9f2596 100644
--- a/pyro_risks/utils/s3.py
+++ b/pyro_risks/utils/s3.py
@@ -134,7 +134,7 @@ def get_file_metadata(self, object_key):
         metadata = obj.metadata
         return metadata
 
-    def get_files_metadata(self, pattern=None):
+    def get_files_metadata(self, pattern:str=None) -> dict:
         """
         Lists files in the S3 bucket with their size in GB and last modified dates.