diff --git a/rosidl_generator_mypy/__init__.py b/rosidl_generator_mypy/__init__.py
index 9da0df8..82acb2c 100644
--- a/rosidl_generator_mypy/__init__.py
+++ b/rosidl_generator_mypy/__init__.py
@@ -165,7 +165,7 @@ def to_type_annotation(
 
         # eg: std_msgs/Header[]
         return Annotation(
-            "typing.Sequence[{}]".format(type_annotation.getter),
+            "typing.MutableSequence[{}]".format(type_annotation.getter),
             "typing.Sequence[{}]".format(type_annotation.setter),
         )