diff --git a/rosidl_generator_py/CMakeLists.txt b/rosidl_generator_py/CMakeLists.txt
index 5f74d58f..fb7fba50 100644
--- a/rosidl_generator_py/CMakeLists.txt
+++ b/rosidl_generator_py/CMakeLists.txt
@@ -76,11 +76,11 @@ if(BUILD_TESTING)
       APPEND_LIBRARY_DIRS "${_append_library_dirs}"
       WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/rosidl_generator_py"
     )
-  endif()
 
-  ament_add_pytest_test(test_cli_extension test/test_cli_extension.py
-    PYTHON_EXECUTABLE "${BUILDTYPE_PYTHON_EXECUTABLE}"
-  )
+    ament_add_pytest_test(test_cli_extension test/test_cli_extension.py
+      PYTHON_EXECUTABLE "${BUILDTYPE_PYTHON_EXECUTABLE}"
+    )
+  endif()
 endif()
 
 ament_package(
diff --git a/rosidl_generator_py/rosidl_generator_py/cli.py b/rosidl_generator_py/rosidl_generator_py/cli.py
index bec5483d..b1d3762c 100644
--- a/rosidl_generator_py/rosidl_generator_py/cli.py
+++ b/rosidl_generator_py/rosidl_generator_py/cli.py
@@ -26,6 +26,14 @@
 
 class GeneratePython(GenerateCommandExtension):
 
+    def __init__(self, name, *, typesupport_implementations=None):
+        super().__init__(name)
+        if typesupport_implementations is None:
+            typesupport_implementations = ['rosidl_typesupport_c']
+            typesupport_implementations.extend(
+                get_resources('rosidl_typesupport_c'))
+        self.__typesupport_implementations = typesupport_implementations
+
     def generate(
         self,
         package_name,
@@ -55,10 +63,6 @@ def generate(
             ))
 
         # Generate code
-        typesupport_implementations = ['rosidl_typesupport_c']
-        typesupport_implementations.extend(
-            get_resources('rosidl_typesupport_c')
-        )
         with legacy_generator_arguments_file(
             package_name=package_name,
             interface_files=idl_interface_files,
@@ -68,4 +72,4 @@ def generate(
         ) as path_to_arguments_file:
             return generate_py(
                 path_to_arguments_file,
-                typesupport_implementations)
+                self.__typesupport_implementations)
diff --git a/rosidl_generator_py/test/test_cli_extension.py b/rosidl_generator_py/test/test_cli_extension.py
index 1fe51b2e..bcc5fbb6 100644
--- a/rosidl_generator_py/test/test_cli_extension.py
+++ b/rosidl_generator_py/test/test_cli_extension.py
@@ -14,15 +14,33 @@
 
 import pathlib
 
+from ament_index_python import get_resources
 from rosidl_cli.command.generate.api import generate
 
 PACKAGE_DIR = str(pathlib.Path(__file__).parent.parent)
 
 
-def test_cli_extension_for_smoke(tmp_path):
-    generate(
-        package_name='rosidl_generator_py',
-        interface_files=[PACKAGE_DIR + ':msg/StringArrays.msg'],
-        types=['py'],
-        output_path=tmp_path
-    )
+def test_cli_extension_for_smoke(tmp_path, capsys):
+    # NOTE(hidmic): pytest and empy do not play along,
+    # the latter expects some proxy will stay in sys.stdout
+    # and the former insists in overwriting it
+    interface_files = [PACKAGE_DIR + ':msg/StringArrays.msg']
+
+    with capsys.disabled():  # so do everything in one run
+        # Passing target typesupport implementations explictly
+        generate(
+            package_name='rosidl_typesupport_py',
+            interface_files=interface_files,
+            types=['py[typesupport_implementations:{}]'.format(
+                list(get_resources('rosidl_typesupport_c'))
+            )],
+            output_path=tmp_path / 'explicit_args'
+        )
+
+        # Using default typesupport implementations
+        generate(
+            package_name='rosidl_typesupport_pu',
+            interface_files=interface_files,
+            types=['py'],
+            output_path=tmp_path / 'defaults'
+        )