diff --git a/aws_lambda_powertools/logging/logger.py b/aws_lambda_powertools/logging/logger.py
index 93e1dd45698..f86833a7851 100644
--- a/aws_lambda_powertools/logging/logger.py
+++ b/aws_lambda_powertools/logging/logger.py
@@ -580,7 +580,7 @@ def debug(
             extra=extra,
         )
 
-    def append_keys(self, **additional_keys) -> None:
+    def append_keys(self, **additional_keys: object) -> None:
         self.registered_formatter.append_keys(**additional_keys)
 
     def remove_keys(self, keys: Iterable[str]) -> None: