diff --git a/tools/idf.py b/tools/idf.py
index e6573f149d..e5a5e77a1e 100755
--- a/tools/idf.py
+++ b/tools/idf.py
@@ -677,7 +677,7 @@ def init_cli(verbose_output=None):
 def main():
     checks_output = check_environment()
     cli = init_cli(verbose_output=checks_output)
-    cli(prog_name=PROG)
+    cli(sys.argv[1:], prog_name=PROG)
 
 
 def _valid_unicode_config():
diff --git a/tools/idf_py_actions/core_ext.py b/tools/idf_py_actions/core_ext.py
index b728dd4e9c..952477a451 100644
--- a/tools/idf_py_actions/core_ext.py
+++ b/tools/idf_py_actions/core_ext.py
@@ -35,7 +35,9 @@ def action_extensions(base_actions, project_path):
         Menuconfig target is build_target extended with the style argument for setting the value for the environment
         variable.
         """
-        os.environ['MENUCONFIG_STYLE'] = style
+        # The subprocess lib cannot accept environment variables as "unicode" . This is a problem
+        # only in Python 2.
+        os.environ['MENUCONFIG_STYLE'] = style.encode(sys.getfilesystemencoding() or 'utf-8')
         build_target(target_name, ctx, args)
 
     def fallback_target(target_name, ctx, args):