diff --git a/pyproject.toml b/pyproject.toml
index ae9f8ae..7abea59 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -29,7 +29,7 @@ dependencies = [
     "pydantic>=2.12; python_version >= '3.14'",
     "aiohttp>=3.10.5; python_version == '3.13'",
     "aiohttp>=3.13; python_version >= '3.14'",
-    "modern-di>=3,<4",
+    "modern-di>=4,<5",
 ]
 version = "0"
 
diff --git a/tests/dependencies.py b/tests/dependencies.py
index 1f2401b..a76a7f3 100644
--- a/tests/dependencies.py
+++ b/tests/dependencies.py
@@ -14,11 +14,8 @@ class DependentCreator:
     dep1: SimpleCreator
 
 
-def fetch_event_type(event: TelegramObject | None = None) -> str:
-    # Optional-with-default so an explicit container.validate() treats the event
-    # as optional (the providers are only registered by setup_di); the real
-    # event still injects at runtime.
-    return type(event).__name__ if event else ""
+def fetch_event_type(event: TelegramObject) -> str:
+    return type(event).__name__
 
 
 class Dependencies(Group):