diff --git a/CHANGELOG.md b/CHANGELOG.md
index c8e5b18..b518edd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## 0.12.3
+
++ Replace `resource_filename()` (from deprecated pkg_resources) with API from `importlib.resources`
+
 ## 0.12.2
 
 + Fix imports in module `sqlalchemy.quart`
diff --git a/src/suou/__init__.py b/src/suou/__init__.py
index b50bb02..eb8c0e3 100644
--- a/src/suou/__init__.py
+++ b/src/suou/__init__.py
@@ -38,7 +38,7 @@ from .http import WantsContentType
 from .color import OKLabColor, chalk, WebColor, RGBColor, LinearRGBColor, XYZColor, OKLCHColor
 from .mat import Matrix
 
-__version__ = "0.12.2"
+__version__ = "0.12.3"
 
 __all__ = (
     'ConfigOptions', 'ConfigParserConfigSource', 'ConfigSource', 'ConfigValue',
diff --git a/src/suou/pkg_resources.py b/src/suou/pkg_resources.py
new file mode 100644
index 0000000..1ad73c9
--- /dev/null
+++ b/src/suou/pkg_resources.py
@@ -0,0 +1,31 @@
+"""
+Drop-in replacement for pkg_resources (kind of), using importlib.resources.
+
+*New in 0.12.3*
+
+---
+
+Copyright (c) 2025 Sakuragasaki46.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+See LICENSE for the specific language governing permissions and
+limitations under the License.
+
+This software is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+"""
+
+
+from importlib.resources import files
+
+def resource_filename(package_name, resource_name: str) -> str:
+    """
+    Backport of resource_filename() from pkg_resources, using importlib.resources
+    """
+    return str(files(package_name) / resource_name)
+
+
+__all__ = (
+    'resource_filename',
+)
\ No newline at end of file
diff --git a/src/suou/sass.py b/src/suou/sass.py
index 092179b..0a84a4b 100644
--- a/src/suou/sass.py
+++ b/src/suou/sass.py
@@ -1,5 +1,17 @@
 """
 
+
+---
+
+Copyright (c) 2025 Sakuragasaki46.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+See LICENSE for the specific language governing permissions and
+limitations under the License.
+
+This software is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 """
 
 
@@ -16,7 +28,7 @@ from .validators import must_be
 from .asgi import _MiddlewareFactory, ASGIApp, ASGIReceive, ASGIScope, ASGISend
 from . import __version__ as _suou_version
 
-from pkg_resources import resource_filename
+from .pkg_resources import resource_filename
 
 logger = logging.getLogger(__name__)