diff --git a/crates/ruff_linter/src/rules/ruff/rules/post_init_default.rs b/crates/ruff_linter/src/rules/ruff/rules/post_init_default.rs
index c587a0f7a2..256e650e68 100644
--- a/crates/ruff_linter/src/rules/ruff/rules/post_init_default.rs
+++ b/crates/ruff_linter/src/rules/ruff/rules/post_init_default.rs
@@ -61,6 +61,12 @@ use super::helpers::{dataclass_kind, DataclassKind};
 /// foo = Foo()  # Prints '1 2'.
 /// ```
 ///
+/// ## Fix safety
+///
+/// This fix is always marked as unsafe because, although switching to `InitVar` is usually correct,
+/// it is incorrect when the parameter is not intended to be part of the public API or when the value
+/// is meant to be shared across all instances.
+///
 /// ## References
 /// - [Python documentation: Post-init processing](https://docs.python.org/3/library/dataclasses.html#post-init-processing)
 /// - [Python documentation: Init-only variables](https://docs.python.org/3/library/dataclasses.html#init-only-variables)