diff --git a/ariadne_codegen/utils.py b/ariadne_codegen/utils.py
index 3225a79c..b52a4d9b 100644
--- a/ariadne_codegen/utils.py
+++ b/ariadne_codegen/utils.py
@@ -78,6 +78,7 @@ def _format_code(code: str, *, remove_unused_imports: bool = True) -> str:
         input=code,
         capture_output=True,
         text=True,
+        encoding="utf-8",
         check=False,
         timeout=_SUBPROCESS_TIMEOUT,
     )
diff --git a/tests/client_generators/test_custom_arguments.py b/tests/client_generators/test_custom_arguments.py
new file mode 100644
index 00000000..3865e5c1
--- /dev/null
+++ b/tests/client_generators/test_custom_arguments.py
@@ -0,0 +1,73 @@
+import ast
+
+from graphql import build_schema
+
+from ariadne_codegen.client_generators.custom_arguments import ArgumentGenerator
+from ariadne_codegen.codegen import generate_import_from
+
+from ..utils import compare_ast
+
+
+def _expected_enum_import(name: str) -> ast.ImportFrom:
+    """Matches generate_import_from for GraphQLEnumType in _parse_graphql_type_name."""
+    return generate_import_from(names=[name], from_="enums", level=1)
+
+
+def test_generate_arguments_records_enums_submodule_import_for_enum_field_argument():
+    schema = build_schema(
+        """
+        schema { query: Query }
+        enum Color { RED GREEN }
+        type Query {
+            paint(color: Color!): String
+        }
+        """
+    )
+    field = schema.query_type.fields["paint"]
+    generator = ArgumentGenerator(custom_scalars={}, convert_to_snake_case=False)
+
+    generator.generate_arguments(field.args)
+
+    expected = _expected_enum_import("Color")
+    assert len(generator.imports) == 1
+    assert compare_ast(generator.imports[0], expected)
+
+
+def test_generate_arguments_records_enums_submodule_import_for_list_of_enum_arguments():
+    schema = build_schema(
+        """
+        schema { query: Query }
+        enum SortOrder { ASC DESC }
+        type Query {
+            items(order: [SortOrder!]!): String
+        }
+        """
+    )
+    field = schema.query_type.fields["items"]
+    generator = ArgumentGenerator(custom_scalars={}, convert_to_snake_case=False)
+
+    generator.generate_arguments(field.args)
+
+    expected = _expected_enum_import("SortOrder")
+    assert len(generator.imports) == 1
+    assert compare_ast(generator.imports[0], expected)
+
+
+def test_generate_arguments_records_enums_submodule_import_for_optional_enum_argument():
+    schema = build_schema(
+        """
+        schema { query: Query }
+        enum Priority { LOW HIGH }
+        type Query {
+            task(priority: Priority): String
+        }
+        """
+    )
+    field = schema.query_type.fields["task"]
+    generator = ArgumentGenerator(custom_scalars={}, convert_to_snake_case=False)
+
+    generator.generate_arguments(field.args)
+
+    expected = _expected_enum_import("Priority")
+    assert len(generator.imports) == 1
+    assert compare_ast(generator.imports[0], expected)
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 42a82331..84e57620 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -1,9 +1,11 @@
 import ast
+import subprocess
 from textwrap import dedent
 
 import pytest
 
 from ariadne_codegen.utils import (
+    _format_code,
     add_extra_to_base_model,
     ast_to_str,
     convert_to_multiline_string,
@@ -78,6 +80,29 @@ class TestClass(Efg):
     assert not_used_imported_class not in generated_code
 
 
+def test_ast_to_str_non_ascii_unicode_round_trip_issue_422():
+    """Regression for mirumee/ariadne-codegen#422 (Windows cp1252 / ruff stdin)."""
+    description = "商店 line: émoji 🛍️ — characters outside cp1252"
+    module = ast.parse(f'"""{description}"""')
+    generated = ast_to_str(module, remove_unused_imports=False)
+    assert description in generated
+
+
+def test_format_code_ruff_format_uses_utf8_encoding_issue_422(mocker):
+    """Ensure ruff format stdin/stdout use UTF-8 (mirumee/ariadne-codegen#422)."""
+    spy = mocker.patch("ariadne_codegen.utils.subprocess.run", wraps=subprocess.run)
+
+    _format_code("x = 1\n")
+
+    format_calls = [
+        call
+        for call in spy.call_args_list
+        if tuple(call[0][0][2:4]) == ("ruff", "format")
+    ]
+    assert format_calls, "expected a ruff format subprocess.run"
+    assert format_calls[-1][1].get("encoding") == "utf-8"
+
+
 @pytest.mark.parametrize(
     "name, expected_result",
     [