---
source: crates/ruff_linter/src/rules/ruff/mod.rs
---
RUF013 [*] PEP 484 prohibits implicit `Optional`
 --> RUF013_1.py:4:12
  |
4 | def f(arg: int = None):  # RUF013
  |            ^^^
5 |     pass
  |
help: Convert to `Optional[T]`
  |
3 |
  - def f(arg: int = None):  # RUF013
4 + from typing import Optional
5 + def f(arg: Optional[int] = None):  # RUF013
6 |     pass
  |
note: This is an unsafe fix and may change runtime behavior
