diff --git a/rosidl_adapter/rosidl_adapter/action/__init__.py b/rosidl_adapter/rosidl_adapter/action/__init__.py
index d4b128079..6e8719b6c 100644
--- a/rosidl_adapter/rosidl_adapter/action/__init__.py
+++ b/rosidl_adapter/rosidl_adapter/action/__init__.py
@@ -32,7 +32,7 @@ def convert_action_to_idl(package_dir, package_name, input_file, output_dir):
     print(f'Writing output file: {abs_output_file}')
     data = {
         'pkg_name': package_name,
-        'relative_input_file': input_file,
+        'relative_input_file': input_file.as_posix(),
         'action': action,
     }
 
diff --git a/rosidl_adapter/rosidl_adapter/msg/__init__.py b/rosidl_adapter/rosidl_adapter/msg/__init__.py
index a054f8b98..b02b7b5bd 100644
--- a/rosidl_adapter/rosidl_adapter/msg/__init__.py
+++ b/rosidl_adapter/rosidl_adapter/msg/__init__.py
@@ -32,7 +32,7 @@ def convert_msg_to_idl(package_dir, package_name, input_file, output_dir):
     print(f'Writing output file: {abs_output_file}')
     data = {
         'pkg_name': package_name,
-        'relative_input_file': input_file,
+        'relative_input_file': input_file.as_posix(),
         'msg': msg,
     }
 
diff --git a/rosidl_adapter/rosidl_adapter/srv/__init__.py b/rosidl_adapter/rosidl_adapter/srv/__init__.py
index 41ae4e053..c57b7013f 100644
--- a/rosidl_adapter/rosidl_adapter/srv/__init__.py
+++ b/rosidl_adapter/rosidl_adapter/srv/__init__.py
@@ -32,7 +32,7 @@ def convert_srv_to_idl(package_dir, package_name, input_file, output_dir):
     print(f'Writing output file: {abs_output_file}')
     data = {
         'pkg_name': package_name,
-        'relative_input_file': input_file,
+        'relative_input_file': input_file.as_posix(),
         'srv': srv,
     }