diff --git a/rclpy/rclpy/node.py b/rclpy/rclpy/node.py
index 425a468bb..ec5576435 100644
--- a/rclpy/rclpy/node.py
+++ b/rclpy/rclpy/node.py
@@ -986,7 +986,7 @@ def list_parameters(
         result = ListParametersResult()
 
         separator_less_than_depth: Callable[[str], bool] = \
-            lambda str: str.count(PARAMETER_SEPARATOR_STRING) < depth
+            lambda s: s.count(PARAMETER_SEPARATOR_STRING) < depth
 
         recursive: bool = \
             (len(prefixes) == 0) and (depth == ListParameters.Request.DEPTH_RECURSIVE)